Add compiler-rt check for FMV Linux tests. (#99)

The patch fixes buildbot failures discovered in
#98 by checking for
compiler-rt availability. Existence of compiler-rt builtin check
was added to find_compiler_rt_library function.

SingleSource/UnitTests/AArch64/CMakeLists.txt

@@ -1,7 +1,10 @@
 if(CMAKE_C_COMPILER_ID STREQUAL "Clang")
   if(TARGET_OS STREQUAL "Linux")
-    list(APPEND CFLAGS --rtlib=compiler-rt)
-    list(APPEND LDFLAGS --rtlib=compiler-rt)
+    find_compiler_rt_library(RTLIB)
+    if (RTLIB)
+      list(APPEND CFLAGS --rtlib=compiler-rt)
+      list(APPEND LDFLAGS --rtlib=compiler-rt)
+    endif()
   endif()
   if(ARCH STREQUAL "AArch64")
     llvm_singlesource(PREFIX "aarch64-")

cmake/modules/HandleCompilerRT.cmake

@@ -32,7 +32,7 @@ function(find_compiler_rt_library variable)
     string(STRIP "${library_file}" library_file)
     file(TO_CMAKE_PATH "${library_file}" library_file)
     get_filename_component(basename ${library_file} NAME)
-    if(basename MATCHES ".*clang_rt\.([a-z0-9_\-]+)\.(a|lib)")
+    if(basename MATCHES ".*clang_rt\.([a-z0-9_\-]+)\.(a|lib)" AND EXISTS ${library_file})
       message(STATUS "Found compiler-rt builtin library: ${basename}")
       set(COMPILER_RT_LIBRARY_builtins_${target} "${basename}" CACHE INTERNAL
         "compiler-rt library for ${target}")
@@ -47,4 +47,5 @@ function(find_compiler_rt_library variable)
   else()
     set(${variable} "" PARENT_SCOPE)
   endif()
-endfunction()
+endfunction()
+