Make all x86 target builds on MSVC use the amd64_x86 toolchain

[zturner]

Summary

x86 builds of libclang.dll are failing with out of memory errors (Example: http://lab.llvm.org:8011/builders/lldb-x86-windows-msvc/builds/14604). This patch is a global change against every MSVC build running on zorg to use the x64 -> x86 cross compilation toolchain when the target is x86, so that the linker will never run out of memory.

This amd64_x86 toolchain was introduced in VS2013 so it's guaranteed to be present on all versions of MSVC that we support.

This was supposed to go to llvm-commits in addition to lldb-commits. Updated subscriber list.

[cray]

The amd64_x86 toolchain is not present on the community edition of visual studio. I am not sure if any build bots use this version though.

[gkistanova]

LGTM

Thanks

Galina

[Eugene.Zelenko]

Committed in r258738.

zorg/buildbot/builders/Util.py

 import buildbot.status.results
 
 def getVisualStudioEnvironment(vs=r"""%VS120COMNTOOLS%""", target_arch=None):
-    arch_arg = {'x86': 'x86', 'x64': 'amd64', 'amd64': 'amd64'}.get(target_arch, '%PROCESSOR_ARCHITECTURE%')
+    # x86 builds should use the 64 bit -> x86 cross compilation toolchain to avoid
+    # out of memory linker errors
+    arch_arg = {'x86': 'amd64_x86', 'x64': 'amd64', 'amd64': 'amd64'}.get(target_arch, '%PROCESSOR_ARCHITECTURE%')
     vcvars_command = "\"" + "\\".join((vs, '..','..','VC', 'vcvarsall.bat')) + "\""
     vcvars_command = "%s %s && set" % (vcvars_command, arch_arg)
     return vcvars_command