GammaRay builds fails after CI updated

Recent CI infra update has caused GammaRay builds to fail, likely this is related to a new feature called "test split". This affects all 5.12, 5.13 and 5.14 branches.

Ubuntu 18.04

agent:2020/02/25 20:03:46 build.go:546: Executing instruction 57 of 58 - ExecuteCommand
agent:2020/02/25 20:03:46 build.go:276: [make] 36000 2700 false false
{{agent:2020/02/25 20:03:46 build.go:253: g++ -Wl,-O1 -Wl,-rpath,/home/qt/work/install/lib -o tests-qt-ci-only /home/qt/work/install/lib/libQt5Gui.so /home/qt/work/install/lib/libQt5Core.so -lGL -lpthread }}
agent:2020/02/25 20:03:46 build.go:253: /usr/lib/x86_64-linux-gnu/crt1.o: In function `_start':
agent:2020/02/25 20:03:46 build.go:253: (.text+0x20): undefined reference to `main'
agent:2020/02/25 20:03:46 build.go:253: collect2: error: ld returned 1 exit status
agent:2020/02/25 20:03:46 build.go:253: Makefile:69: recipe for target 'tests-qt-ci-only' failed

MacOS

agent:2020/02/25 20:08:07 build.go:546: Executing instruction 61 of 62 - ExecuteCommand
agent:2020/02/25 20:08:07 build.go:276: [make] 36000 2700 false false
{{agent:2020/02/25 20:08:08 build.go:253: /Applications/Xcode10.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++ -stdlib=libc++ -headerpad_max_install_names -arch x86_64 -Wl,-syslibroot,/Applications/Xcode10.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk -mmacosx-version-min=10.13 -Wl,-rpath,@executable_path/../Frameworks -Wl,-rpath,/Users/qt/work/install/lib -o tests-qt-ci-only.app/Contents/MacOS/tests-qt-ci-only -F/Users/qt/work/install/lib -framework QtGui -framework AppKit -framework Metal -framework QtCore -framework DiskArbitration -framework IOKit -framework OpenGL -framework AGL }}
agent:2020/02/25 20:08:08 build.go:253: Undefined symbols for architecture x86_64:
agent:2020/02/25 20:08:08 build.go:253: "_main", referenced from:
agent:2020/02/25 20:08:08 build.go:253: implicit entry/start for main executable
agent:2020/02/25 20:08:08 build.go:253: ld: symbol(s) not found for architecture x86_64
agent:2020/02/25 20:08:08 build.go:253: clang: error: linker command failed with exit code 1 (use -v to see invocation)
agent:2020/02/25 20:08:08 build.go:253: make: *** [tests-qt-ci-only.app/Contents/MacOS/tests-qt-ci-only] Error 1
agent:2020/02/25 20:08:08 build.go:304: Process finished with error: exit status 2

Windows 10

agent:2020/02/25 20:16:32 build.go:546: Executing instruction 62 of 63 - ExecuteCommand
agent:2020/02/25 20:16:32 build.go:276: [jom] 36000 2700 false false
agent:2020/02/25 20:16:32 build.go:253: jom 1.1.2 - empower your cores
agent:2020/02/25 20:16:32 build.go:253: C:\Utils\Jom\jom.exe -f Makefile.Release
agent:2020/02/25 20:16:32 build.go:253: link /NOLOGO /DYNAMICBASE /NXCOMPAT /OPT:REF /INCREMENTAL:NO /SUBSYSTEM:WINDOWS "/MANIFESTDEPENDENCY:type='win32' name='Microsoft.Windows.Common-Controls' version='6.0.0.0' publicKeyToken='6595b64144ccf1df' language='' processorArchitecture=''" /MANIFEST:embed /OUT:release\tests-qt-ci-only.exe @C:\Users\qt\AppData\Local\Temp\tests-qt-ci-only.exe.5868.0.jom
agent:2020/02/25 20:16:32 build.go:253: LINK : warning LNK4001: no object files specified; libraries used
agent:2020/02/25 20:16:32 build.go:253: LINK : warning LNK4068: /MACHINE not specified; defaulting to X64
agent:2020/02/25 20:16:32 build.go:253: LINK : error LNK2001: unresolved external symbol WinMainCRTStartup
agent:2020/02/25 20:16:32 build.go:253: release\tests-qt-ci-only.exe : fatal error LNK1120: 1 unresolved externals
agent:2020/02/25 20:16:32 build.go:253: jom: C:\Users\qt\work\KDAB\GammaRay\tests\Makefile.Release [release\tests-qt-ci-only.exe] Error 1120
agent:2020/02/25 20:16:32 build.go:253: jom: C:\Users\qt\work\KDAB\GammaRay\tests\Makefile [release] Error 2