[configure/make] Propagate names of build host tools when making Buil…

…dTools

When cross-compiling LLVM itself the configure/make scripts get confused when
creating the needed build host tools.  For example, building and configuring
like:

  CC_FOR_BUILD='i686-pc-linux-gnu-gcc' CXX_FOR_BUILD='i686-pc-linux-gnu-g++'
  CXX='i686-mingw32-g++' CC='i686-mingw32-gcc' LD='i686-mingw32-ld' /scratch
  /meadori/llvm-trunk/src/trunk/configure --host=i686-mingw32

  CC_FOR_BUILD='i686-pc-linux-gnu-gcc' CXX_FOR_BUILD='i686-pc-linux-gnu-g++'
  CXX='i686-mingw32-g++' CC='i686-mingw32-gcc' LD='i686-mingw32-ld' make

causes the following build break:

  checking whether the C compiler works... configure: error: cannot run C
  compiled programs.
  If you meant to cross compile, use `--host'.
  See `config.log' for more details.

The 'config.log' shows that i686-mingw32-gcc is being used to create
executables for the build host.

This patch fixes the problem by propogating the names of the build host
tools via BUILD_* when configuring/making BuildTools.

Original patch by Ekaterina Sanina.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204760 91177308-0d34-0410-b5e6-96231b3b80d8

Makefile

@@ -112,6 +112,11 @@ cross-compile-build-tools:
 	  cd BuildTools ; \
 	  unset CFLAGS ; \
 	  unset CXXFLAGS ; \
+	  AR=$(BUILD_AR) ; \
+	  AS=$(BUILD_AS) ; \
+	  LD=$(BUILD_LD) ; \
+	  CC=$(BUILD_CC) ; \
+	  CXX=$(BUILD_CXX) ; \
 	  unset SDKROOT ; \
 	  unset UNIVERSAL_SDK_PATH ; \
 	  configure_opts= ; \