[Bug 40385] New: usp10:usp10 regression caused by new cross-compiler

https://bugs.winehq.org/show_bug.cgi?id=40385

Bug ID: 40385
           Summary: usp10:usp10 regression caused by new cross-compiler
           Product: Wine
           Version: 1.9.6
          Hardware: x86
                OS: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: usp10
          Assignee: [e-mail]
          Reporter: [e-mail]

The WineHQ upgrade changed the cross-compiler used to generate the reference
WineTest executables. Since the upgrade the usp10:usp10 64 bit test has this
failure on Windows Vista to Windows 10:

usp10.c:3087: Test failed: ScriptStringCPtoX should return E_INVALIDARG not
00000000

See:
https://test.winehq.org/data/tests/usp10:usp10.html
https://www.winehq.org/pipermail/wine-devel/2016-March/112371.html

I can reproduce the problem with this compiler:
$ i686-w64-mingw32-gcc --version
i686-w64-mingw32-gcc (GCC) 5.3.1 20160205

But if I recompile the tests with -O0 the failures go away which points to a
compiler bug.
We need to either:
* Switch to a non buggy compiler to build the reference WineTest executables.
  (which might involve reporting the bug in the first place)

* Add 'CFLAGS = -g -O0' to the test's Makefile.in as a workaround.
  (preferably once we can point to a relevant compiler bug)

* Find some other nicer workaround in the C file.