Cannot compile C++ projects on Mac OS X with Qbs 1.11 after upgrading to Xcode 9.3

After upgrading to Xcode 9.3 my C++ projects won't compile anymore. Any of them. I get fatal errors on standard C++ include files, for example "type_traits", "chrono", "cstdint" etc.

Here's a dump of the output when compiling a simple project:

15:18:05: Running steps for project cpptests...

compiling systemtime.cpp

compiling main.cpp

generating Info.plist for cpptests

/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++ -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk -g -O0 -Wall -Wextra -target x86_64-apple-macosx-macho -pipe -fexceptions -fvisibility=default -fPIC -I/Users/catalinm2/Workspace/CppProjects/cpptests -I/Users/catalinm2/Workspace/CppProjects/cpptests/include -std=c++11 -o /Users/catalinm2/Workspace/CppProjects/build-cpptests-Desktop_Qt_5_9_4_clang_64bit2-Debug/qtc_Desktop_Qt_5_9_4_clang_64bit2_Debug/cpptests.2ea1dffd/3a52ce780950d4d9/systemtime.cpp.o -c /Users/catalinm2/Workspace/CppProjects/cpptests/systemtime.cpp

In file included from /Users/catalinm2/Workspace/CppProjects/cpptests/systemtime.cpp:3:

/Users/catalinm2/Workspace/CppProjects/cpptests/systemtime.h:18:10: fatal error: 'cstdint' file not found

#include <cstdint>

^~~~~~~~~

1 error generated.

Process failed with exit code 1.

The following products could not be built for configuration qtc_Desktop_Qt_5_9_4_clang_64bit2_Debug:

cpptests

Error while building/deploying project cpptests (kit: Desktop Qt 5.9.4 clang 64bit2)

When executing step "Qbs Build"

15:18:05: Elapsed time: 00:01.

It looks like the system includes paths are not properly set anymore.