Build failure on OS X 10.11: "C compiler cannot create executables"

[apjanke]

I'm getting a build failure on my OS X 10.11 Public Beta machine with Xcode 7 GM installed.

$ ./configure
[...]
checking for APR-util... yes
checking for gcc... /Applications/Xcode.app/Contents/Developer/Toolchains/OSX10.11.xctoolchain/usr/bin/cc
checking for C compiler default output file name... configure: error: C compiler cannot create executables
See `config.log' for more details.

My configure logs are here: https://gist.github.com/apjanke/8b1c7ebb84e9176ae310

It might be that this configure is not getting Xcode's internal path structure right. Here's an excerpt from that config.log.

configure:2676: checking for C compiler default output file name
configure:2679: /Applications/Xcode.app/Contents/Developer/Toolchains/OSX10.11.xctoolchain/usr/bin/cc    -DDARWIN -DSIGPROCMASK_SETS_THREAD_MASK -DDARWIN_10   conftest.c  >&5
./configure: line 2680: /Applications/Xcode.app/Contents/Developer/Toolchains/OSX10.11.xctoolchain/usr/bin/cc: No such file or directory

But that OSX10.11.xctoolchain doesn't exist. This Xcode.app is Xcode 7 GM. I checked Xcode 6.2 and 5.0.2 on OS X 10.9.5, and they only have XcodeDefault.xctoolchain, too.

[/Applications/Xcode.app/Contents/Developer/Toolchains]
$ ls
XcodeDefault.xctoolchain
[/Applications/Xcode.app/Contents/Developer/Toolchains]
$