[Bug target/57753] New: FSF gcc bootstrap needs to use xcrun to bootstrap post-darwin12

[howarth at nitro dot med.uc.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57753

            Bug ID: 57753
           Summary: FSF gcc bootstrap needs to use xcrun to bootstrap
                    post-darwin12
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: howarth at nitro dot med.uc.edu

The WWDC "What’s New in the LLVM Compiler" video on
https://developer.apple.com/wwdc/videos/ indicated that the SDK will be moved
out of / on future releases after Mountain Lion and that the proper way to find
the headers, previously in /usr/include and
/System/Library/Frameworks/*.framework/Headers is to use the xcrun tool on
darwin to access the compiler...

     xcrun provides a means to locate or invoke coexistence- and platform-aware
developer tools from the com-
     mand-line, without requiring users to modify makefiles or otherwise take
inconvenient measures to support
     multiple Xcode tool chains.

     The tool xcode-select is used to specify which installation of Xcode is
used, and may be overridden by the
     DEVELOPER_DIR environment variable.

     The SDK defaults to the boot system OS SDK, and can be specified by the
SDKROOT environment variable or the
     -sdk option (which takes precedences over SDKROOT).

So the configure scripts for bootstrapping on darwin will need to be adjusted
to call compilers during the build using the xcrun command...

     xcrun <tool_name> [<tool_arguments>]

We don't need to pass '-sdk SDK' as xcrun defaults to the deployment SDK. FYI,
this change can be tested on Mac OS X 10.7/10.8 using Xcode 4.6.3 by performing
the following steps...

sudo mv /usr/include /usr/include.off
sudo mv /System/Library/Frameworks/CoreFoundation.framework/Headers
/System/Library/Frameworks/CoreFoundation.framework/Headers.off

Note that the CoreFoundation.framework headers are used by the libasan build on
darwin.