Removing __linux__ definition in CMake

Removing this definition as this should already be defined by compiler.
This is causing compile errors on newer versions of llvm because the
macro is being redefined.

Change-Id: Ica6a06f46a14e16d3f52e83b9b5ee8cfd7359510


[ROCm/ROCR-Runtime commit: e4fffa140a]

projects/rocr-runtime/runtime/hsa-runtime-tools/CMakeLists.txt

@@ -22,7 +22,7 @@ list ( APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/../cmake_modules" )
 include ( utils )
 
 ## Compiler preproc definitions.
-add_definitions ( -D__linux__ )
+#add_definitions ( -D__linux__ )
 add_definitions ( -DUNIX_OS )
 add_definitions ( -DLINUX )
 add_definitions ( -D__AMD64__ )