Don't try to strip llc (it was removed in 5ae9322) (WebAssembly#76)

Author: sbc100

Makefile

@@ -147,7 +147,7 @@ build/config.BUILT:
 build: build/llvm.BUILT build/wasi-libc.BUILT build/compiler-rt.BUILT build/libcxxabi.BUILT build/libcxx.BUILT build/config.BUILT
 
 strip: build/llvm.BUILT
-	cd $(PREFIX)/bin; strip clang-9 llc lld llvm-ar
+	cd $(PREFIX)/bin; strip clang-9 lld llvm-ar
 
 package: build/package.BUILT