add run-make test to ensure using rust-lld works

using the `-C linker-flavor=gcc:lld -C link-self-contained=linker` stable flags

Author: lqd

src/test/run-make/rust-lld/Makefile

@@ -0,0 +1,15 @@
+# only-linux
+# only-x86_64
+# needs-rust-lld
+
+# Ensure that the stable version of `-Zgcc-ld=lld` works:
+# - `-C link-self-contained=linker`
+# - `-C linker-flavor=gcc:lld`
+
+-include ../../run-make-fulldeps/tools.mk
+RUSTC_FLAGS = -C linker-flavor=gcc:lld -C link-self-contained=linker -Z unstable-options -C link-args=-Wl,-v
+
+all:
+	RUSTC_LOG=rustc_codegen_ssa::back::link=info $(RUSTC) $(RUSTC_FLAGS) empty.rs 2> $(TMPDIR)/output.txt
+	$(CGREP) "lib/rustlib/x86_64-unknown-linux-gnu/bin/gcc-ld/ld" < $(TMPDIR)/output.txt
+	$(CGREP) -e "^LLD [0-9]+\.[0-9]+\.[0-9]+" < $(TMPDIR)/output.txt

src/test/run-make/rust-lld/empty.rs

@@ -0,0 +1 @@
+fn main() {}