Make rustc's host triple agree with the build system's

Makefile.in

@@ -198,7 +198,7 @@ endif
 
 STAGE$(1) := $$(Q)$$(call CFG_RUN_TARG,stage$(1), \
                 $$(CFG_VALGRIND_COMPILE$(1)) stage$(1)/bin/rustc$$(X) \
-                $$(CFG_RUSTC_FLAGS) --target=$(2))
+                $$(CFG_RUSTC_FLAGS))
 endef
 
 FUZZ := stage1/bin/fuzzer$(X)

mk/tests.mk

@@ -189,7 +189,7 @@ CTEST_COMMON_ARGS$(2) := --compile-lib-path stage$(2)/lib \
                          --run-lib-path stage$(2)/lib/$$(CFG_HOST_TRIPLE) \
                          --rustc-path stage$(2)/bin/rustc$$(X) \
                          --stage-id stage$(2) \
-                         --rustcflags "--target=$$(CFG_HOST_TRIPLE) $$(CFG_RUSTC_FLAGS)" \
+                         --rustcflags "$$(CFG_RUSTC_FLAGS)" \
                          $$(CTEST_TESTARGS) \
 
 CFAIL_ARGS$(2) := $$(CTEST_COMMON_ARGS$(2)) \

src/comp/driver/rustc.rs

@@ -309,7 +309,15 @@ fn build_target_config(sopts: @session::options) -> @session::config {
 }
 
 fn host_triple() -> str {
-    str::str_from_cstr(llvm::llvm::LLVMRustGetHostTriple())
+    // Get the host triple out of the build environment. This ensures that our
+    // idea of the host triple is the same as for the set of libraries we've
+    // actually built.  We can't just take LLVM's host triple because they
+    // normalize all ix86 architectures to i386.
+    // FIXME: Instead of grabbing the host triple we really should be
+    // grabbing (at compile time) the target triple that this rustc is
+    // built with and calling that (at runtime) the host triple.
+    let ht = #env("CFG_HOST_TRIPLE");
+    ret ht != "" ? ht : fail "rustc built without CFG_HOST_TRIPLE";
 }
 
 fn build_session_options(binary: str, match: getopts::match)