Fix building Hermes from source on Windows failing on the JSI_DIR path

[YevheniiKotyrlo]

Summary:

Building Hermes from source on Windows fails in hermes-engine:configureBuildForHermes, also inside the Visual Studio developer environment its NMake generator needs (reported in #37770):

CMake Error at cmake/modules/Hermes.cmake:160 (add_executable):
  Syntax error in cmake code when parsing string

    C:\work\contributions\react-native\packages\react-native\ReactCommon\jsi/jsi/test/testlib.cpp

  Invalid character escape '\w'.

hermes-engine/build.gradle.kts passes -DJSI_DIR as a native Windows path, and CMake reads its backslashes as escape sequences. This passes the path with forward slashes at both -DJSI_DIR sites, the host hermesc configure and the Android externalNativeBuild. On macOS and Linux the path is unchanged.

Changelog:

[ANDROID] [FIXED] - Fix building Hermes from source on Windows failing on the JSI_DIR path

Test Plan:

On Windows 11, inside the Visual Studio developer environment, with -Preact.internal.useHermesNightly=false so that Hermes builds from source:

• gradlew :packages:react-native:ReactAndroid:hermes-engine:buildHermesC: on main it fails with the error above; with this change it builds hermesc.exe.
• gradlew :packages:react-native:ReactAndroid:hermes-engine:assembleDebug -PreactNativeArchitectures=x86_64: with only the host site changed, configureCMakeRelease[x86_64] fails with the same error; with both, the AAR builds with jni/x86_64/libhermesvm.so.

[cipolleschi]

thanks for fixing this.

[meta-codesync]

@cipolleschi has imported this pull request. If you are a Meta employee, you can view this in D124993090.