[Bug 40442] New: Unexplained new random comctl32:header failure (cross-compiler issue?)

https://bugs.winehq.org/show_bug.cgi?id=40442

Bug ID: 40442
           Summary: Unexplained new random comctl32:header failure
                    (cross-compiler issue?)
           Product: Wine
           Version: 1.9.6
          Hardware: x86
                OS: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: comctl32
          Assignee: [e-mail]
          Reporter: [e-mail]

comctl32:header started having regular failures on newtb-wxppro right after the
WineHQ upgrade (2016/03/17).

https://test.winehq.org/data/tests/comctl32:header.html

The failure:
header.c:1148: Test failed: expected 0, got 1

Things that point to a cross-compiling issue:
 * Since 2016/03/18 comctl32:header has had an almost systematic failure on
newtb-wxppro (68.7%) and more rarely on newtb-w2003std (12.5%).
 * In the 27 runs from 2016/02/09 to 2016/03/17 it had no failure (neither on
these two platforms nor on any other).
 * There has been no change to comctl32:header before it started failing. 
 * The tests that run before comctl32:header don't seem to have undergone
changes that could cause the following tests to fail (see 'git log
62277fb7779f..6bc0ce26a853 dlls/[abc]*/tests').

Unexplained mysteries:
 * Cross-compiling the test with i686-w64-mingw32-gcc (GCC) 5.3.1 20160205, the
standard '-g -O2' options and uploading it to the TestBot does not yield the
expected failure (changing that to '-g -O0' does not make a difference either).
 * None of the other platforms is affected.
 * And even more strange, newtb-xppro is the only Windows XP to be affected by
the new failure.