Updates tryrun.cmake for cross build (#837)

Fix cross build:
```
...
-- Performing Test UNGETC_NOT_RETURN_EOF
CMake Error: TRY_RUN() invoked in cross-compiling mode, please set the following cache variables appropriately:
   UNGETC_NOT_RETURN_EOF_EXITCODE (advanced)
   UNGETC_NOT_RETURN_EOF_EXITCODE__TRYRUN_OUTPUT (advanced)
For details see /home/viewizard/Desktop/diagnostics/artifacts/obj/Linux.armel.Release/TryRunResults.cmake
-- Performing Test UNGETC_NOT_RETURN_EOF - Success
...
```
Related to cmake changes (starts from 3.14.0-rc3, https://gitlab.kitware.com/cmake/cmake/commit/92d9ec9bfb61d2cd35a82d6906de86c71350b865)
More info: https://gitlab.kitware.com/cmake/cmake/issues/18973

diff --git a/eng/cross/tryrun.cmake b/eng/cross/tryrun.cmake
index 988a59c5f6b98cc2f7ecba68bce4efcc7a1c5a36..f841f56b83b49d12d8d85ad4a49a1ef76b114bee 100644 (file)
--- a/eng/cross/tryrun.cmake
+++ b/eng/cross/tryrun.cmake
@@ -3,6 +3,7 @@ set(TARGET_ARCH_NAME $ENV{TARGET_BUILD_ARCH})
 
 macro(set_cache_value)
   set(${ARGV0} ${ARGV1} CACHE STRING "Result from TRY_RUN" FORCE)
+  set(${ARGV0}__TRYRUN_OUTPUT "dummy output" CACHE STRING "Output from TRY_RUN" FORCE)
 endmacro()
 
 if(EXISTS ${CROSS_ROOTFS}/usr/lib/gcc/armv6-alpine-linux-musleabihf OR