Add deployment knobs to tests (for Apple platforms)

The tests for libc++ specify -target on the command-line to the
compiler, but this is problematic for a few reasons.

Firstly, the -target option isn't supported on Apple platforms. Parts
of the triple get dropped and ignored. Instead, software should be
compiled with a combination of the -arch and -m<name>-version-min
options.

Secondly, the generic "darwin" target references a kernel version
instead of a platform version. Each platform has its own independent
versions (with different versions of libc++.1.dylib), independent of the
version of the Darwin kernel.

This commit adds support to the LIT infrastructure for testing against
Apple platforms using -arch and -platform options.

If the host is not on OS X, or the compiler type is not clang or apple-clang, then this commit has NFC.
If the host is on OS X and --param=target_triple=... is specified, then a warning is emitted to use arch and platform instead. Besides the warning, there's NFC.
If the host is on OS X and *no* target-triple is specified, then use the new deployment target logic. This uses two new lit parameters, --param=arch=<arch> and --param=platform=<platform>. <platform> has the form <name>[<version>].
By default, arch is auto-detected from clang -dumpmachine, and platform is "macosx".
If the platform doesn't have a version:
For "macosx", the version is auto-detected from the host system using sw_vers. This may give a different version than the SDK, since new SDKs can be installed on older hosts.
Otherwise, the version is auto-detected from the SDK version using xcrun --show-sdk-path.
-arch <arch> -m<name>-version-min=<version> is added to the compiler flags.
The target triple is computed as <arch>-apple-<platform>. It is *not* passed to clang, but it is available for XFAIL and UNSUPPORTED (as is with_system_cxx_lib=<target>).
For convenience, apple-darwin and <arch>-apple-darwin are added to the set of available features.
There were a number of tests marked to XFAIL on x86_64-apple-darwin11
and x86_64-apple-darwin12. I updated these to
x86_64-apple-macosx10.7 and x86_64-apple-macosx10.8.

llvm-svn: 297798
diff --git a/libcxx/test/std/strings/string.conversions/stof.pass.cpp b/libcxx/test/std/strings/string.conversions/stof.pass.cpp
index 1e17e1d..aeef0dd 100644
--- a/libcxx/test/std/strings/string.conversions/stof.pass.cpp
+++ b/libcxx/test/std/strings/string.conversions/stof.pass.cpp
@@ -7,8 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// XFAIL: with_system_cxx_lib=x86_64-apple-darwin11
-// XFAIL: with_system_cxx_lib=x86_64-apple-darwin12
+// XFAIL: with_system_cxx_lib=x86_64-apple-macosx10.7
+// XFAIL: with_system_cxx_lib=x86_64-apple-macosx10.8
 
 // <string>
 
diff --git a/libcxx/test/std/strings/string.conversions/stol.pass.cpp b/libcxx/test/std/strings/string.conversions/stol.pass.cpp
index 457cf0a..f01bbf8 100644
--- a/libcxx/test/std/strings/string.conversions/stol.pass.cpp
+++ b/libcxx/test/std/strings/string.conversions/stol.pass.cpp
@@ -7,8 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// XFAIL: with_system_cxx_lib=x86_64-apple-darwin11
-// XFAIL: with_system_cxx_lib=x86_64-apple-darwin12
+// XFAIL: with_system_cxx_lib=x86_64-apple-macosx10.7
+// XFAIL: with_system_cxx_lib=x86_64-apple-macosx10.8
 
 // <string>
 
diff --git a/libcxx/test/std/strings/string.conversions/stoll.pass.cpp b/libcxx/test/std/strings/string.conversions/stoll.pass.cpp
index ca8412a..b823ab7 100644
--- a/libcxx/test/std/strings/string.conversions/stoll.pass.cpp
+++ b/libcxx/test/std/strings/string.conversions/stoll.pass.cpp
@@ -7,8 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// XFAIL: with_system_cxx_lib=x86_64-apple-darwin11
-// XFAIL: with_system_cxx_lib=x86_64-apple-darwin12
+// XFAIL: with_system_cxx_lib=x86_64-apple-macosx10.7
+// XFAIL: with_system_cxx_lib=x86_64-apple-macosx10.8
 
 // <string>
 
diff --git a/libcxx/test/std/strings/string.conversions/stoul.pass.cpp b/libcxx/test/std/strings/string.conversions/stoul.pass.cpp
index 1acdf11..5e1f696 100644
--- a/libcxx/test/std/strings/string.conversions/stoul.pass.cpp
+++ b/libcxx/test/std/strings/string.conversions/stoul.pass.cpp
@@ -7,8 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// XFAIL: with_system_cxx_lib=x86_64-apple-darwin11
-// XFAIL: with_system_cxx_lib=x86_64-apple-darwin12
+// XFAIL: with_system_cxx_lib=x86_64-apple-macosx10.7
+// XFAIL: with_system_cxx_lib=x86_64-apple-macosx10.8
 
 // <string>
 
diff --git a/libcxx/test/std/strings/string.conversions/stoull.pass.cpp b/libcxx/test/std/strings/string.conversions/stoull.pass.cpp
index e63679e..70563d9 100644
--- a/libcxx/test/std/strings/string.conversions/stoull.pass.cpp
+++ b/libcxx/test/std/strings/string.conversions/stoull.pass.cpp
@@ -7,8 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// XFAIL: with_system_cxx_lib=x86_64-apple-darwin11
-// XFAIL: with_system_cxx_lib=x86_64-apple-darwin12
+// XFAIL: with_system_cxx_lib=x86_64-apple-macosx10.7
+// XFAIL: with_system_cxx_lib=x86_64-apple-macosx10.8
 
 // <string>