[PATCH] Use correct export_dynamic_flag_spec for PE-COFF $hosts

[Charles Wilson]

* libltdl/m4/libtool.m4 (_LT_LINKER_SHLIBS) [cygwin*|mingw*|pw32*|cegcc*]:
Define export_dynamic_flag_spec as -Wl,--export-all-symbols, as required
by GNU ld for PE-COFF.

Original patch by Yaakov Selkowitz. As he explained:

On Cygwin, the --export-all-symbols linker flag is required;
 --export-dynamic has no effect
(see http://sourceware.org/bugzilla/show_bug.cgi?id=6744).

This patch fixes two problems:

(1) LT_SYS_DLOPEN_SELF returns a false negative;
(2) Using the -export-dynamic libtool flag does not affect the
   resulting binary.

Tested in combination with several other cygwin patches, as part of the
recent cygwin "official" 2.2.7a-N libtool release(s):
http://cygwin.com/ml/cygwin-announce/2009-03/msg00080.html
http://cygwin.com/ml/cygwin-announce/2009-03/msg00081.html

No regressions.  Okay to push?

---
 libltdl/m4/libtool.m4 |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/libltdl/m4/libtool.m4 b/libltdl/m4/libtool.m4
index 477f6e3..15612c0 100644
--- a/libltdl/m4/libtool.m4
+++ b/libltdl/m4/libtool.m4
@@ -4275,6 +4275,7 @@ _LT_EOF
       # _LT_TAGVAR(hardcode_libdir_flag_spec, $1) is actually meaningless,
       # as there is no search path for DLLs.
       _LT_TAGVAR(hardcode_libdir_flag_spec, $1)='-L$libdir'
+      _LT_TAGVAR(export_dynamic_flag_spec, $1)='${wl}--export-all-symbols'
       _LT_TAGVAR(allow_undefined_flag, $1)=unsupported
       _LT_TAGVAR(always_export_symbols, $1)=no
       _LT_TAGVAR(enable_shared_with_static_runtimes, $1)=yes
-- 
1.6.1.2