Update two options to my proposed syntax for user-facing driver options:

  -gcc-toolchain foo  ->  --gcc-toolchain=foo
  -target foo         ->  --target=foo

I've added legacy aliases for the original spellings. I've updated the
canonical tests to check both spellings, and switched all of the
-gcc-toolchain usages elsewhere in the test suite to use the new one.
I've updated some of the usages of -target to the new syntax, but will
finish that in a separate entirely mechanical change once I'm sure this
won't get rolled back for some reason (It touches a *huge* number of RUN
lines in the test suite unsurprisingly).

A nice result is that the three most common flags I end up using when
doing cross compiles are all now consistent: --target=, --sysroot=, and
--gcc-toolchain=.

llvm-svn: 184408
diff --git a/clang/test/Driver/gcc-toolchain.cpp b/clang/test/Driver/gcc-toolchain.cpp
index e122dac..b8c0572 100644
--- a/clang/test/Driver/gcc-toolchain.cpp
+++ b/clang/test/Driver/gcc-toolchain.cpp
@@ -1,7 +1,13 @@
 // Test that gcc-toolchain option is working correctly
 //
 // RUN: %clangxx -no-canonical-prefixes %s -### -o %t 2>&1 \
-// RUN:     -target i386-unknown-linux \
+// RUN:     --target=i386-unknown-linux \
+// RUN:     --gcc-toolchain=%S/Inputs/ubuntu_11.04_multiarch_tree/usr \
+// RUN:   | FileCheck %s
+//
+// Additionally check that the legacy spelling of the flag works.
+// RUN: %clangxx -no-canonical-prefixes %s -### -o %t 2>&1 \
+// RUN:     --target=i386-unknown-linux \
 // RUN:     -gcc-toolchain %S/Inputs/ubuntu_11.04_multiarch_tree/usr \
 // RUN:   | FileCheck %s
 //