CMakeLists: Use MATCHES not STREQUAL for compiler conditionals

Apparently there's "Clang" and "AppleClang".

CMAKE_CXX_COMPILER_ID MATCHES "Clang"
matches against both, where as STREQUAL will not consider "AppleClang" as a match.

Bug: b/130343040
Bug: b/130335507
Change-Id: I3d09a726924a7bbf8dc061349fc9fa504f7d08e2
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/29868
Tested-by: Ben Clayton <bclayton@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index e2c4ba5..0e9bf2b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -237,7 +237,7 @@
         "-Werror=missing-braces"
     )
 
-    if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
         list(APPEND SWIFTSHADER_COMPILE_OPTIONS
             "-Werror=unused-lambda-capture"
             "-Werror=string-conversion"