[OpenMP][libomp] Fix CMake version symbol testing

Do not check for version symbol support if the necessary linker flag is
not supported.

Differential Revision: https://reviews.llvm.org/D143200

(cherry picked from commit c32022a)

Author: Jonathan Peyton

openmp/runtime/cmake/config-ix.cmake

@@ -246,7 +246,11 @@ endif()
 
 # Checking features
 # Check if version symbol assembler directives are supported
-libomp_check_version_symbols(LIBOMP_HAVE_VERSION_SYMBOLS)
+if (LIBOMP_HAVE_VERSION_SCRIPT_FLAG)
+  libomp_check_version_symbols(LIBOMP_HAVE_VERSION_SYMBOLS)
+else()
+  set(LIBOMP_HAVE_VERSION_SYMBOLS FALSE)
+endif()
 
 # Check if quad precision types are available
 if(CMAKE_C_COMPILER_ID STREQUAL "GNU")

openmp/runtime/src/exports_test_so.txt

@@ -19,10 +19,6 @@ VERSION {
 
         *;         # All symbols as exported for testing.
 
-    local: # Non-exported symbols.
-
-        *;         # All other symbols are not exported.
-
 }; # VERSION
 
 # sets up GCC OMP_ version dependency chain