[ruby-core:71461] [Ruby trunk - Bug #11680] [Open] LD_PRELOAD setting causes child process crash on mingw

Issue #11680 has been reported by Hiroshi Shirosaki.

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Bug #11680: LD_PRELOAD setting causes child process crash on mingw
https://bugs.ruby-lang.org/issues/11680

* Author: Hiroshi Shirosaki
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: ruby 2.3.0dev (2015-11-11 trunk 47767) [x64-mingw32]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
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I see make test-all failures on mingw with msys2.

```
TestMiniTestUnitTestCase#test_assert_equal_different_long =       0 [main] diff 8736 C:\Users\h.shirosaki\work\rubyinsta
ller\sandbox\devkit\usr\bin\diff.exe: *** fatal error - error while loading shared libraries: C: cannot open shared obje
ct file: No such file or directory
    434 [main] diff 8736 cygwin_exception::open_stackdumpfile: Dumping stack trace to diff.exe.stackdump
      0 [main] diff 8048 C:\Users\h.shirosaki\work\rubyinstaller\sandbox\devkit\usr\bin\diff.exe: *** fatal error - erro
r while loading shared libraries: C: cannot open shared object file: No such file or directory
    388 [main] diff 8048 cygwin_exception::open_stackdumpfile: Dumping stack trace to diff.exe.stackdump
0.06 s = F
```

diff.exe of msys2 crashed.
LD_PRELOAD is set in tool/runruby.rb on test-all. If I set `ENV['LD_PRELOAD'] = nil`, diff.exe doesn't crash.
LD_PRELOAD may not usable on msys2(cygwin).


```
diff --git a/configure.in b/configure.in
index 0d253a9..e97871d 100644
--- a/configure.in
+++ b/configure.in
@@ -3126,6 +3126,7 @@ if test "$with_dln_a_out" != yes; then
 			XLDFLAGS="$XLDFLAGS -Wl,--stack,0x00200000,--enable-auto-import"
 			DLDFLAGS="${DLDFLAGS} -Wl,--enable-auto-image-base,--enable-auto-import"
 			: ${LIBPATHENV=""}
+			: ${PRELOADENV=""}
 			rb_cv_dlopen=yes],
 	[hiuxmpp], [	: ${LDSHARED='$(LD) -r'}],
 	[atheos*], [	: ${LDSHARED='$(CC) -shared'}
```



-- 
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