Add timeout to execute_process() in CMAKE_DETERMINE_COMPILER_ID().

In CMAKE_DETERMINE_COMPILER_ID_VENDOR() the compiler is called with various
arguments. In some cases, this can make the compiler hang and wait
forever for input (e.g. "as -v"). That's why add an timeout
so it terminates finally. 10 seconds should be more than enough,
this is the time it takes to startup the compiler, which is
usually quite fast.

Alex

Modules/CMakeDetermineCompilerId.cmake

@@ -283,6 +283,7 @@ FUNCTION(CMAKE_DETERMINE_COMPILER_ID_VENDOR lang)
       WORKING_DIRECTORY ${CMAKE_${lang}_COMPILER_ID_DIR}
       OUTPUT_VARIABLE output ERROR_VARIABLE output
       RESULT_VARIABLE result
+      TIMEOUT 10
       )
     IF("${output}" MATCHES "${regex}")
       FILE(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
@@ -291,9 +292,15 @@ FUNCTION(CMAKE_DETERMINE_COMPILER_ID_VENDOR lang)
       SET(CMAKE_${lang}_COMPILER_ID "${vendor}" PARENT_SCOPE)
       BREAK()
     ELSE()
-      FILE(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
-        "Checking whether the ${lang} compiler is ${vendor} using \"${flags}\" "
-        "did not match \"${regex}\":\n${output}")
+      IF("${result}" MATCHES  "timeout")
+        FILE(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
+          "Checking whether the ${lang} compiler is ${vendor} using \"${flags}\" "
+          "terminated after 10 s due to timeout.")
+      ELSE()
+        FILE(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
+          "Checking whether the ${lang} compiler is ${vendor} using \"${flags}\" "
+          "did not match \"${regex}\":\n${output}")
+       ENDIF()
     ENDIF()
   ENDFOREACH()
 ENDFUNCTION(CMAKE_DETERMINE_COMPILER_ID_VENDOR)