[BUILD] Enable RCCL build with amdclang++ (#1128)

Signed-off-by: nileshnegi <Nilesh.Negi@amd.com>

toolchain-linux.cmake

@@ -7,13 +7,12 @@ else()
 endif()
 
 if (NOT DEFINED ENV{CXX})
-  set(CMAKE_CXX_COMPILER "${rocm_bin}/hipcc" CACHE PATH "Path to the C++ compiler")
+  set(CMAKE_CXX_COMPILER "${rocm_bin}/amdclang++" CACHE PATH "Path to the C++ compiler")
 else()
   set(CMAKE_CXX_COMPILER "$ENV{CXX}" CACHE PATH "Path to the C++ compiler")
 endif()
 
-if (NOT DEFINED ENV{CC})
-  set(CMAKE_C_COMPILER "${rocm_bin}/hipcc" CACHE PATH "Path to the C compiler")
-else()
-  set(CMAKE_C_COMPILER "$ENV{CC}" CACHE PATH "Path to the C compiler")
+if (NOT DEFINED ENV{CXXFLAGS})
+  set(CMAKE_CXX_FLAGS_DEBUG "-g -O1")
+  set(CMAKE_CXX_FLAGS_RELEASE "-O3")
 endif()