I just tried and have the same issue with Qt 5.2.1, so perhaps this is an issue with my particular setup, I am not sure.

The configure script crashes with this output:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++ -c -o msvc_nmake.o -pipe -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk -mmacosx-version-min=10.6 -g -fconstant-cfstrings -MMD -g -I/Users/ezust/Qt/5.3.0-beta/qtbase/qmake -I/Users/ezust/Qt/5.3.0-beta/qtbase/qmake/library -I/Users/ezust/Qt/5.3.0-beta/qtbase/qmake/generators -I/Users/ezust/Qt/5.3.0-beta/qtbase/qmake/generators/unix -I/Users/ezust/Qt/5.3.0-beta/qtbase/qmake/generators/win32 -I/Users/ezust/Qt/5.3.0-beta/qtbase/qmake/generators/mac -I/Users/ezust/Qt/5.3.0-beta/qtbase/qmake/generators/integrity -I/Users/ezust/Qt/5.3.0-beta/qtbase/include -I/Users/ezust/Qt/5.3.0-beta/qtbase/include/QtCore -I/Users/ezust/Qt/5.3.0-beta/qtbase/include/QtCore/5.3.0 -I/Users/ezust/Qt/5.3.0-beta/qtbase/include/QtCore/5.3.0/QtCore -I/Users/ezust/Qt/5.3.0-beta/qtbase/src/corelib/global -DHAVE_QCONFIG_CPP -I/Users/ezust/Qt/5.3.0-beta/qtbase/mkspecs/macx-clang -I/Users/ezust/Qt/5.3.0-beta/qtbase/tools/shared -DQT_BUILD_QMAKE -DQT_BOOTSTRAPPED -DPROEVALUATOR_FULL -DQT_NO_TEXTCODEC -DQT_NO_UNICODETABLES -DQT_NO_COMPONENT -DQT_NO_COMPRESS -DQT_NO_THREAD -DQT_NO_QOBJECT -DQT_NO_GEOM_VARIANT -DQT_NO_DATASTREAM -DQT_CRYPTOGRAPHICHASH_ONLY_SHA1 -DQT_JSON_READONLY /Users/ezust/Qt/5.3.0-beta/qtbase/qmake/generators/win32/msvc_nmake.cpp
0 clang 0x00000001017b9c3f main + 24869327
1 clang 0x00000001017b9f64 main + 24870132
2 libsystem_platform.dylib 0x00007fff8f3125aa _sigtramp + 26
3 libsystem_platform.dylib 0x0000000103d55ad0 _sigtramp + 1956918592
4 clang 0x000000010006caeb main + 436347
5 clang 0x000000010006c8eb main + 435835
6 clang 0x000000010087c719 main + 8889513
7 clang 0x000000010087be1b main + 8887211
8 clang 0x00000001001d8ea8 main + 1928248
9 clang 0x00000001001d3e24 main + 1907636
10 clang 0x00000001001dea31 main + 1951681
11 clang 0x00000001001de8ba main + 1951306
12 clang 0x00000001001d8e94 main + 1928228
13 clang 0x00000001001d3e24 main + 1907636
14 clang 0x00000001001e3011 main + 1969569
15 clang 0x00000001001ee2c5 main + 2015317
16 clang 0x00000001001edb07 main + 2013335
17 clang 0x00000001001eda5d main + 2013165
18 clang 0x00000001001e9dfd main + 1997709
19 clang 0x00000001001e99fb main + 1996683
20 clang 0x0000000100212e2a main + 2165690
21 clang 0x00000001001e9dac main + 1997628
22 clang 0x00000001001eb955 main + 2004709
23 clang 0x00000001001e99fb main + 1996683
24 clang 0x0000000100212e2a main + 2165690
25 clang 0x00000001001e9dac main + 1997628
26 clang 0x00000001001eb955 main + 2004709
27 clang 0x00000001001e99fb main + 1996683
28 clang 0x0000000100212e2a main + 2165690
29 clang 0x00000001001e9dac main + 1997628
30 clang 0x00000001001eb955 main + 2004709
31 clang 0x00000001001cc50b main + 1876635
32 clang 0x000000010019ecb3 main + 1690179
33 clang 0x000000010019e180 main + 1687312
34 clang 0x00000001000be3ac main + 770364
35 clang 0x00000001000944c9 main + 598617
36 clang 0x00000001000942ff main + 598159
37 clang 0x00000001000941b4 main + 597828
38 clang 0x000000010005ea02 main + 378770
39 clang 0x000000010005b814 main + 365988
40 clang 0x000000010005a6c5 main + 361557
41 clang 0x0000000100026f9d main + 150829
42 clang 0x0000000100007ec0 main + 23632
43 libdyld.dylib 0x00007fff8cc355fd start + 1
Stack dump:
0. Program arguments: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -cc1 -triple x86_64-apple-macosx10.6.0 -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -main-file-name msvc_nmake.cpp -mrelocation-model pic -pic-level 2 -mdisable-fp-elim -masm-verbose -munwind-tables -target-cpu core2 -target-linker-version 224.1 -g -coverage-file /Users/ezust/Qt/5.3.0-beta/qtbase/qmake/msvc_nmake.o -resource-dir /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/5.0 -dependency-file msvc_nmake.d -MT msvc_nmake.o -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk -D HAVE_QCONFIG_CPP -D QT_BUILD_QMAKE -D QT_BOOTSTRAPPED -D PROEVALUATOR_FULL -D QT_NO_TEXTCODEC -D QT_NO_UNICODETABLES -D QT_NO_COMPONENT -D QT_NO_COMPRESS -D QT_NO_THREAD -D QT_NO_QOBJECT -D QT_NO_GEOM_VARIANT -D QT_NO_DATASTREAM -D QT_CRYPTOGRAPHICHASH_ONLY_SHA1 -D QT_JSON_READONLY -I /Users/ezust/Qt/5.3.0-beta/qtbase/qmake -I /Users/ezust/Qt/5.3.0-beta/qtbase/qmake/library -I /Users/ezust/Qt/5.3.0-beta/qtbase/qmake/generators -I /Users/ezust/Qt/5.3.0-beta/qtbase/qmake/generators/unix -I /Users/ezust/Qt/5.3.0-beta/qtbase/qmake/generators/win32 -I /Users/ezust/Qt/5.3.0-beta/qtbase/qmake/generators/mac -I /Users/ezust/Qt/5.3.0-beta/qtbase/qmake/generators/integrity -I /Users/ezust/Qt/5.3.0-beta/qtbase/include -I /Users/ezust/Qt/5.3.0-beta/qtbase/include/QtCore -I /Users/ezust/Qt/5.3.0-beta/qtbase/include/QtCore/5.3.0 -I /Users/ezust/Qt/5.3.0-beta/qtbase/include/QtCore/5.3.0/QtCore -I /Users/ezust/Qt/5.3.0-beta/qtbase/src/corelib/global -I /Users/ezust/Qt/5.3.0-beta/qtbase/mkspecs/macx-clang -I /Users/ezust/Qt/5.3.0-beta/qtbase/tools/shared -fdeprecated-macro -fdebug-compilation-dir /Users/ezust/Qt/5.3.0-beta/qtbase/qmake -ferror-limit 19 -fmessage-length 80 -stack-protector 1 -mstackrealign -fblocks -fobjc-runtime=macosx-10.6.0 -fobjc-dispatch-method=mixed -fobjc-default-synthesize-properties -fencode-extended-block-signature -fcxx-exceptions -fexceptions -fdiagnostics-show-option -fcolor-diagnostics -o msvc_nmake.o -x c++ /Users/ezust/Qt/5.3.0-beta/qtbase/qmake/generators/win32/msvc_nmake.cpp
1. /Users/ezust/Qt/5.3.0-beta/qtbase/qmake/generators/win32/msvc_nmake.cpp:232:1: current parser token 'void'
2. /Users/ezust/Qt/5.3.0-beta/qtbase/qmake/generators/win32/msvc_nmake.cpp:72:25: LLVM IR generation of declaration 'NmakeMakefileGenerator::writeMakefile'
3. /Users/ezust/Qt/5.3.0-beta/qtbase/qmake/generators/win32/msvc_nmake.cpp:72:25: Generating code for declaration 'NmakeMakefileGenerator::writeMakefile'
4. /Users/ezust/Qt/5.3.0-beta/qtbase/qmake/generators/win32/msvc_nmake.cpp:80:45: LLVM IR generation of compound statement ('{}')
5. /Users/ezust/Qt/5.3.0-beta/qtbase/qmake/generators/win32/msvc_nmake.cpp:85:38: LLVM IR generation of compound statement ('{}')
6. /Users/ezust/Qt/5.3.0-beta/qtbase/qmake/generators/win32/msvc_nmake.cpp:87:51: LLVM IR generation of compound statement ('{}')
clang: error: unable to execute command: Segmentation fault: 11
clang: error: clang frontend command failed due to signal (use -v to see invocation)
Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn)
Target: x86_64-apple-darwin13.1.0
Thread model: posix
clang: note: diagnostic msg: PLEASE submit a bug report to http://developer.apple.com/bugreporter/ and include the crash backtrace, preprocessed source, and associated run script.
clang: note: diagnostic msg:
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang: note: diagnostic msg: /var/folders/w8/7b8_hn3s1q5__mmk774qctwc0000gn/T/msvc_nmake-3nD9Sn.cpp
clang: note: diagnostic msg: /var/folders/w8/7b8_hn3s1q5__mmk774qctwc0000gn/T/msvc_nmake-3nD9Sn.sh
clang: note: diagnostic msg:

********************
make: *** [msvc_nmake.o] Error 254
[ezust@icsmac] /Users/ezust/Qt/5.3.0-beta>