CheckCSourceRuns: Teach CHECK_C_SOURCE_RUNS to log run output

Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Fixes: #17745

Modules/CheckCSourceRuns.cmake

@@ -92,7 +92,8 @@ macro(CHECK_C_SOURCE_RUNS SOURCE VAR)
       CMAKE_FLAGS -DCOMPILE_DEFINITIONS:STRING=${MACRO_CHECK_FUNCTION_DEFINITIONS}
       -DCMAKE_SKIP_RPATH:BOOL=${CMAKE_SKIP_RPATH}
       "${CHECK_C_SOURCE_COMPILES_ADD_INCLUDES}"
-      COMPILE_OUTPUT_VARIABLE OUTPUT)
+      COMPILE_OUTPUT_VARIABLE OUTPUT
+      RUN_OUTPUT_VARIABLE RUN_OUTPUT)
     # if it did not compile make the return value fail code of 1
     if(NOT ${VAR}_COMPILED)
       set(${VAR}_EXITCODE 1)
@@ -104,8 +105,10 @@ macro(CHECK_C_SOURCE_RUNS SOURCE VAR)
         message(STATUS "Performing Test ${VAR} - Success")
       endif()
       file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
-        "Performing C SOURCE FILE Test ${VAR} succeeded with the following output:\n"
+        "Performing C SOURCE FILE Test ${VAR} succeeded with the following compile output:\n"
         "${OUTPUT}\n"
+        "...and run output:\n"
+        "${RUN_OUTPUT}\n"
         "Return value: ${${VAR}}\n"
         "Source file was:\n${SOURCE}\n")
     else()
@@ -119,8 +122,10 @@ macro(CHECK_C_SOURCE_RUNS SOURCE VAR)
         message(STATUS "Performing Test ${VAR} - Failed")
       endif()
       file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
-        "Performing C SOURCE FILE Test ${VAR} failed with the following output:\n"
+        "Performing C SOURCE FILE Test ${VAR} failed with the following compile output:\n"
         "${OUTPUT}\n"
+        "...and run output:\n"
+        "${RUN_OUTPUT}\n"
         "Return value: ${${VAR}_EXITCODE}\n"
         "Source file was:\n${SOURCE}\n")