winuwp x86 release build fails due to IDL build step

[Holo-Krzysztof]

Applies to branch Sergej/20181206-m71-python of webrtc-uwp-sdk.

When preparing and building only the winuwp x86 release build without the wrapper, the process fails at the end when doing zsLib/IDL related things.
As far as I understand, the IDL is only needed when building the wrapper, so it might be good to omit that step when --noWrapper is specified. A workaround is to build debug first, then release which produces functional builds for both configs.

Steps to reproduce:

• Clone webrtc-uwp-sdk and checkout the right branch
• git submodule update --init
• In powershell, cd to scripts folder
• python .\run.py -a prepare -t webrtc -p winuwp --cpus x86 -c release --noWrapper
• python .\run.py -a build -t webrtc -p winuwp --cpus x86 -c release --noWrapper

Here's the error log:

===================================== Script execution STARTED =====================================

[INFO    ] - [System         ] - __updateDepotToolsPath         - Adding depot tools path 'C:\webrtc-uwp-sdk\scripts\..\.\webrtc\xplatform\depot_tools' to the PATH. (system.py:333)
[INFO    ] - [System         ] - __determineVisualStudioPath    - Visual studio path is C:\Program Files (x86)\Microsoft Visual Studio\2017\Community (system.py:401)
[DEBUG   ] - [System         ] - __determineVisualStudioPath    - MSVC tools path is C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC (system.py:402)
[DEBUG   ] - [System         ] - __determineVisualStudioPath    - MSVC tools bin path is C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.16.27023\bin\Hostx64 (system.py:403)
[INFO    ] - [Main           ] - main                           - Root logger is created (run.py:172)
[DEBUG   ] - [System         ] - checkIfTargetsAreSupported     - Checking if specified targets are supported. (system.py:172)
[DEBUG   ] - [System         ] - checkIfPlatformsAreSupported   - Checking if specified platforms are supported. (system.py:197)

===================================== Build webrtc winuwp x86 release STARTED =====================================

[INFO    ] - [Build          ] - run                            - Running build for target: webrtc; platform: winuwp; cpu: x86; configuration: release (builder.py:40)
[DEBUG   ] - [Utility        ] - pushd                          - pushd C:\webrtc-uwp-sdk\scripts\..\.\webrtc\xplatform\webrtc\.\out\webrtc_winuwp_x86_release (utility.py:293)
[INFO    ] - [Build          ] - buildTargets                   - Following targets ['webrtc', 'third_party/jsoncpp:jsoncpp', 'rtc_base:rtc_json'] will be built for cpu x86 (builder.py:148)
[DEBUG   ] - [Build          ] - buildTargets                   - Building target webrtc (builder.py:154)
[DEBUG   ] - [Utility        ] - runSubprocess                  - Running subprocess:
C:\webrtc-uwp-sdk\scripts\..\.\webrtc\xplatform\depot_tools\ninja.exe webrtc (utility.py:476)
[1/1] Regenerating ninja files
[2957/3007] ACTION //sdk/windows:webrtc_idl(//build/toolchain/win:uwp_clang_x86)
FAILED: ../../sdk/windows/wrapper/generated/cx/cx_Helpers.cpp ../../sdk/windows/wrapper/generated/cx/cx_Helpers.h
C:/Python27/python.exe ../../third_party/idl/zsLib-eventing/runIDLCompiler.py ../../sdk/idl/config.json webrtcIdlCompiledFlag.flg x86 ../windows "c dotnet json cx json wrapper python cppwinrt msidl" x64
runIDLCompiler - idlCompilationFPath: C:\webrtc-uwp-sdk\webrtc\xplatform\webrtc\third_party\idl\zsLib-eventing/webrtcIdlCompiledFlag.flg
Running idl compilation
runIDLCompiler - idlPath: ../../sdk/idl/config.json
runIDLCompiler - jsonFile: config.json
runIDLCompiler - idlAlreadyCompletedFlagFile: webrtcIdlCompiledFlag.flg
runIDLCompiler - NewWorkingPath:C:\webrtc-uwp-sdk\webrtc\xplatform\webrtc\sdk\idl
runIDLCompiler - compilerFullPath: C:\webrtc-uwp-sdk\webrtc\xplatform\webrtc\out\webrtc_winuwp_x86_release/x86/zslib-eventing-tool-compiler.exe
runIDLCompiler - command: C:\webrtc-uwp-sdk\webrtc\xplatform\webrtc\out\webrtc_winuwp_x86_release/x86/zslib-eventing-tool-compiler.exe -idl c dotnet json cx json wrapper python cppwinrt msidl -c config.json -o ../windows
Failed idl compilation-1073740791
[2958/3007] ACTION //third_party/idl/zsLib:zslib_events(//build/toolchain/win:uwp_x86)
FAILED: uwp_x86/obj/third_party/idl/zsLib/{source_name_part}
C:/Python27/python.exe ../../third_party/idl/zsLib-eventing/runEventCompiler.py ../../third_party/idl/zsLib/zsLib/cpp/zsLib.events.json x86 x64
('Event compilation flag path: ', 'C:\\webrtc-uwp-sdk\\webrtc\\xplatform\\webrtc\\third_party\\idl\\zsLib-eventing/zsLib.events_eventsCompiled.flg')
Running events compilation for ../../third_party/idl/zsLib/zsLib/cpp/zsLib.events.json
Failed event compilation-1073740791
ninja: build stopped: subcommand failed.
[ERROR   ] - [Utility        ] - runSubprocess                  - Subprocess execution has failed! (utility.py:498)
[DEBUG   ] - [Build          ] - buildTargets                   - Building target third_party/jsoncpp:jsoncpp (builder.py:154)
[DEBUG   ] - [Build          ] - buildTargets                   - Building target rtc_base:rtc_json (builder.py:154)
[DEBUG   ] - [Utility        ] - popd                           - popd C:\webrtc-uwp-sdk\scripts (utility.py:302)

====================================== Failed building webrtc winuwp x86 release ENDED ======================================


========================================= SUMMARY =========================================

ACTION: build
         FAILED: webrtc   winuwp   x86   release      execution time: 0:09:30.343000

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