make sure LDFLAGS are propagated as well

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

src/cc/CMakeLists.txt

@@ -14,7 +14,7 @@ add_definitions(${LLVM_DEFINITIONS})
 configure_file(libbcc.pc.in ${CMAKE_CURRENT_BINARY_DIR}/libbcc.pc @ONLY)
 
 # prune unused llvm static library stuff when linking into the new .so
-set(CMAKE_SHARED_LINKER_FLAGS "-Wl,--exclude-libs=ALL")
+set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,--exclude-libs=ALL")
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC")
 set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fPIC")