Removed compiler limitiation of FindGccAtomic.cmake. It's also needed/used for llvm/clang.

cmake/Modules/FindGccAtomic.cmake

 # This scripts finds gcc's built-in atomic shared library (libatomic.so).
 # It is required to link against this library on gcc when using 16 byte atomics, even when running on x86_64/amd64.
 
-if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
-
-  FIND_LIBRARY(GCCLIBATOMIC_LIBRARY NAMES atomic atomic.so.1 libatomic.so.1
-    HINTS
-    $ENV{HOME}/local/lib64
-    $ENV{HOME}/local/lib
-    /usr/local/lib64
-    /usr/local/lib
-    /opt/local/lib64
-    /opt/local/lib
-    /usr/lib64
-    /usr/lib
-    /lib64
-    /lib
-  )
-
-else ()
-
-  SET(GCCLIBATOMIC_LIBRARY "")
-
-endif ()
+FIND_LIBRARY(GCCLIBATOMIC_LIBRARY NAMES atomic atomic.so.1 libatomic.so.1
+  HINTS
+  $ENV{HOME}/local/lib64
+  $ENV{HOME}/local/lib
+  /usr/local/lib64
+  /usr/local/lib
+  /opt/local/lib64
+  /opt/local/lib
+  /usr/lib64
+  /usr/lib
+  /lib64
+  /lib
+)
 
 include(FindPackageHandleStandardArgs)
 FIND_PACKAGE_HANDLE_STANDARD_ARGS(GCCLIBATOMIC DEFAULT_MSG GCCLIBATOMIC_LIBRARY)
-