i686-pc-mingw cross build on linux

[Gene Smith <gds@chartertn.net>]

I have successfully built insight 6.8 on linux using installed mingw32 
tools and copied the insight.exe to windows and it runs OK. (I haven't 
tried copying over all the many other installed files to make sure they 
work, which I will do later.) However, the build process on linux has 
some glitches that I solved with some kludges.

The main problem was that during compile it was unable to find 
tk/xlib/X11/X.h. This was because TK_XINCLUDE was blank. This was 
because gdb/configure was finding the system tkConfig.sh file to use at 
/usr/local/lib/ instead of the one produced by insight build. The system 
file has the macro TK_XINCLUDES='' which prevents the include of X.h and 
kills the build. It is not clear to me how to control this. So I just 
changed two places in my insight_sources/gdb/configure file to hardcode 
the TKCONFIG and TCLCONFIG values to insight's tkConfig.sh and 
tclConfig.sh like this with absolute paths:

line 23293 (approx):
     no_tk=
     # gds (kluge)
  ac_cv_c_tkconfig="/home/gene/4.9.1-rtems/archive/insight_build/tk/win"
     TKCONFIG=${ac_cv_c_tkconfig}/tkConfig.sh

line 23177 (approx):
     no_tcl=
     # gds (kluge)
ac_cv_c_tclconfig="/home/gene/4.9.1-rtems/archive/insight_build/tcl/win"
     TCLCONFIG=${ac_cv_c_tclconfig}/tclConfig.sh

There must be a way to correctly insure that insight's own 
tk/tclConfig.sh files are found at insight_build/tcl/win and 
insight_build/tk/win.

Also, during the build the "resource compiler" i686-pc-mingw32-windres 
was never assigned to the macro "RC" which resulted in cryptic errors 
saying "command o could not be found." The only way I could find to fix 
this was to
export RC="i686-pc-mingw32-windres"
before doing configure. I don't know why this macro remains blank if you 
don't do this. Other similar macros get filled in properly.

(This is not a problem doing a mingw build on windows/cygwin with 
-mno-cygwin gcc option. I assume this is because on my windows 
installation only Insight provides the tk/tclConfig.sh files.)

With these fixes, the make and install on linux (fedora 8) works OK and 
the exe runs on XP. I have not copied over the other installed files and 
tried them.

Also, have not tried the cvs HEAD version, only insight release 6.8.

-gene
P/S: My linux mingw32 is built with this script from mingw project (rpms 
not available for fedora8 afaik):
http://sourceforge.net/project/showfiles.php?group_id=2435&package_id=12644