Allow passing RTLIB=compiler-rt to make

Not all linux users will have libatomic installed.
When using clang as the system compiler with compiler-rt as the default
runtime library instead of libgcc, atomic builtins may be provided by compiler-rt.
This change allows such users to pass RTLIB=compiler-rt to make sure
the build doesn't error out on the missing (unnecessary) libatomic.

closes https://github.com/official-stockfish/Stockfish/pull/3597

No functional change

diff --git a/src/Makefile b/src/Makefile
index bf3c3560bbd8efa375d3cc62eac520d173c86813..1d972cffc281c43dd10a299d806bdc3f15a5206f 100644 (file)
--- a/src/Makefile
+++ b/src/Makefile
@@ -386,10 +386,12 @@ ifeq ($(COMP),clang)
        ifneq ($(KERNEL),Darwin)
        ifneq ($(KERNEL),OpenBSD)
        ifneq ($(KERNEL),FreeBSD)
+       ifneq ($(RTLIB),compiler-rt)
                LDFLAGS += -latomic
        endif
        endif
        endif
+       endif
 
        ifeq ($(arch),$(filter $(arch),armv7 armv8))
                ifeq ($(OS),Android)