Ignore cross-lang-lto test for LLVM versions without ThinLTO.

Author: michaelwoerister

src/test/run-make/cross-lang-lto/Makefile

@@ -1,9 +1,12 @@
+
+# min-llvm-version 4.0
+
+-include ../../run-make-fulldeps/tools.mk
+
 # This test makes sure that the expected .llvmbc sections for use by
 # linker-based LTO are available in object files when compiling with
 # -Z cross-lang-lto
 
--include ../../run-make-fulldeps/tools.mk
-
 LLVMBC_SECTION_NAME=\\.llvmbc
 
 ifeq ($(UNAME),Darwin)