qmake configure.json tests appear to be executing the wrong qmake

 g++ -c -pipe -g -std=c++1z -fvisibility=hidden -fvisibility-inlines-hidden -Wall -Wextra -Wvla -Wno-missing-field-initializers -D_REENTRANT -fPIC -DQT_NO_LINKED_LIST -DQT_NO_JAVA_STYLE_ITERATORS -DQT_NO_USING_NAMESPACE -DQT_NO_FOREACH -DQFLOAT16_INCLUDE_FAST -DELF_INTERPRETER=\"/lib64/ld-linux-x86-64.so.2\" -DQT_NO_NARROWING_CONVERSIONS_IN_CONNECT -DQT_BUILD_CORE_LIB -DQT_BUILDING_QT -DQT_NO_CAST_TO_ASCII -DQT_ASCII_CAST_WARNINGS -DQT_MOC_COMPAT -DQT_USE_QSTRINGBUILDER -DQT_DEPRECATED_WARNINGS -DQT_DISABLE_DEPRECATED_BEFORE=0x050000 -DQT_DEPRECATED_WARNINGS_SINCE=0x060000 -D_LARGEFILE64_SOURCE -D_LARGEFILE_SOURCE -DPCRE2_CODE_UNIT_WIDTH=16 -Wall -Wextra -Werror -Woverloaded-virtual -Wshadow -Wundef -Wfloat-equal -Wnon-virtual-dtor -Wpointer-arith -Wformat-security -Wno-long-long -Wno-variadic-macros -pedantic-errors -Wchar-subscripts -Wold-style-cast -Wcast-align -Wzero-as-null-pointer-constant -I/home/fanda/proj/qt5/qtbase/src/corelib -I. -Iglobal -I/home/fanda/proj/qt5/qtbase/src/3rdparty/md5 -I/home/fanda/proj/qt5/qtbase/src/3rdparty/md4 -I/home/fanda/proj/qt5/qtbase/src/3rdparty/sha3 -I/home/fanda/proj/qt5/qtbase/src/3rdparty/harfbuzz/src -I/home/fanda/proj/qt5/qtbase/src/3rdparty/forkfd -I/home/fanda/proj/qt5/qtbase/src/3rdparty/tinycbor/src -I../../include -I../../include/QtCore -I../../include/QtCore/5.14.0 -I../../include/QtCore/5.14.0/QtCore -I.moc -I.tracegen -I/home/fanda/proj/qt5/qtbase/src/3rdparty/pcre2/src -isystem /usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include -I/home/fanda/proj/qt5/qtbase/mkspecs/linux-g++ -DQT_NO_CAST_TO_ASCII=1 -DQT_NO_CAST_FROM_ASCII=1 -UQT_RESTRICTED_CAST_FROM_ASCII -DQT_STRICT_ITERATORS -DQT_NO_URL_CAST_FROM_STRING=1 -DQT_NO_CAST_FROM_BYTEARRAY=1 -DQT_NO_KEYWORDS=1 -DQT_USE_QSTRINGBUILDER -DQT_USE_FAST_OPERATOR_PLUS -Dsignals=int -Dslots=int -Demit=public: -Dforeach=public: -Dforever=public: -xc++ /home/fanda/proj/qt5/qtbase/src/corelib/thread/qsemaphore.h -o .obj/header_qsemaphore.o
 In file included from ../../include/QtCore/qglobal.h:1,
 from /home/fanda/proj/qt5/qtbase/src/corelib/thread/qsemaphore.h:43:
 ../../include/QtCore/../../../../../qt5/qtbase/src/corelib/thread/qbasicatomic.h: In instantiation of 'class QBasicAtomicInteger<long long unsigned int>':
 /home/fanda/proj/qt5/qtbase/src/corelib/thread/qsemaphore.h:70:39: required from here
 ../../include/QtCore/../../../../../qt5/qtbase/src/corelib/global/qglobal.h:121:63: error: static assertion failed: template parameter is an integral of a size not supported on this platform
 # define Q_STATIC_ASSERT_X(Condition, Message) static_assert(bool(Condition), Message)
 ^~~~~~~~~~~~~~~
 ../../include/QtCore/../../../../../qt5/qtbase/src/corelib/thread/qbasicatomic.h:97:5: note: in expansion of macro 'Q_STATIC_ASSERT_X'
 Q_STATIC_ASSERT_X(QAtomicOpsSupport<sizeof(T)>::IsSupported, "template parameter is an integral of a size not supported on this platform");
 ^~~~~~~~~~~~~~~~~
 make[3]: *** [Makefile:15095: .obj/header_qsemaphore.o] Error 1
 make[3]: Leaving directory '/home/fanda/proj/_build/qt5.14/qtbase/src/corelib'
 make[2]: *** [Makefile:200: sub-corelib-make_first] Error 2
 make[2]: Leaving directory '/home/fanda/proj/_build/qt5.14/qtbase/src'
 make[1]: *** [Makefile:51: sub-src-make_first] Error 2
 make[1]: Leaving directory '/home/fanda/proj/_build/qt5.14/qtbase'
 make: *** [Makefile:91: module-qtbase-make_first] Error 2
 [~/proj/_build/qt5.14]$ g++ --version 
 g++ (Debian 8.3.0-6) 8.3.0
 Copyright (C) 2018 Free Software Foundation, Inc.
 This is free software; see the source for copying conditions. There is NO
 warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.