RFA: Improve 128-bit long double configure test

[Daniel Jacobowitz]

MontaVista builds both cross compilers (Linux or Windows -> MVL
target) and native compilers (MVL host) on their Linux-based build
systems.  We discovered that the two compilers disagreed on the
size of long double for PowerPC.  Have I mentioned that I think
making ABI choices based on configure tests is a really lousy idea?

This is the best I could think of to solve the problem.  Configure
wants to grep through /usr/include; if we're building with $build
!= $host (and $host = $target is assured by the previous test, above
the context of the diff), then ask GCC where glibc's headers are.

What do you think?  Is the approach OK?  How about the shell scripting
choices?

-- 
Daniel Jacobowitz
CodeSourcery

2007-11-15  Daniel Jacobowitz  <dan@codesourcery.com>

	* configure.ac: For $build != $host, use the preprocessor to
	find glibc headers.
	* configure: Regenerate.

Index: configure.ac
===================================================================
--- configure.ac	(revision 129996)
+++ configure.ac	(working copy)
@@ -3392,6 +3392,8 @@ AC_CACHE_CHECK(__stack_chk_fail in targe
 	else
 	  glibc_header_dir="${with_sysroot}/usr/include"
 	fi
+      elif test x$build != x$host && test x$GCC = xyes; then
+	glibc_header_dir=`echo "#include <features.h>" | $CPP -x c - | sed '/features/ { s,/features.h".*,,; s,.*",,; q }; d'`
       else
 	glibc_header_dir=/usr/include
       fi
@@ -3446,6 +3448,8 @@ case "$target" in
 	else
 	  glibc_header_dir="${with_sysroot}/usr/include"
 	fi
+      elif test x$build != x$host && test x$GCC = xyes; then
+	glibc_header_dir=`echo "#include <features.h>" | $CPP -x c - | sed '/features/ { s,/features.h".*,,; s,.*",,; q }; d'`
       else
 	glibc_header_dir=/usr/include
       fi