libffi: Add -mno-compact-eh when compiling for Mips

Fix compilation on Mips. Resolve issues detected here:
    http://autobuild.buildroot.net/results/f0c9db496233f53c26e92294d7305aa4511ec7b3/
    http://autobuild.buildroot.net/results/8968690c248df86b040218867f92b573721e872c/
    http://autobuild.buildroot.net/results/a35db8e6a49d022133b486b12f6a8e40b3c95b6e/

Also remove previous special case handling defined in libffi.mk.

[Thomas: add Signed-off-by from Jérôme inside the patch itself.]
Signed-off-by: Jérôme Pouiller <jezz@sysmic.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/libffi/libffi-002-Fix-use-of-compact-eh-frames-on-MIPS.patch

@@ -0,0 +1,27 @@
+Newer MIPS toolchains use a different (compact) eh_frame format.
+libffi don't like them, so we have to switch to the older format.
+
+This patch add -mno-compact-eh to CFLAGS when compiling for
+Mips and compiler support it.
+
+Signed-off-by: Jérôme Pouiller <jezz@sysmic.org>
+
+--- a/configure.ac	2013-08-08 14:53:11.884267155 +0200
++++ b/configure.ac	2013-08-08 14:54:14.437493244 +0200
+@@ -430,6 +430,16 @@
+ AM_CONDITIONAL(FFI_EXEC_TRAMPOLINE_TABLE, test x$FFI_EXEC_TRAMPOLINE_TABLE = x1)
+ AC_SUBST(FFI_EXEC_TRAMPOLINE_TABLE)
+ 
++if test x$TARGET = xMIPS; then
++    save_CFLAGS="$CFLAGS"
++    CFLAGS=-mno-compact-eh
++    AC_MSG_CHECKING([whether the C compiler needs -mno-compact-eh])
++    AC_COMPILE_IFELSE([AC_LANG_PROGRAM([])],
++                      [AC_MSG_RESULT([yes])]; [save_CFLAGS="$save_CFLAGS -mno-compact-eh"],
++                      [AC_MSG_RESULT([no])])
++    CFLAGS="$save_CFLAGS"
++fi
++
+ if test x$TARGET = xX86_64; then
+     AC_CACHE_CHECK([assembler supports unwind section type],
+ 	libffi_cv_as_x86_64_unwind_section_type, [

package/libffi/libffi.mk

@@ -11,12 +11,6 @@ LIBFFI_LICENSE_FILES = LICENSE
 LIBFFI_INSTALL_STAGING = YES
 LIBFFI_AUTORECONF = YES
 
-# Newer CS MIPS toolchains use a different (compact) eh_frame format
-# libffi don't like them, just switch to the older format
-ifeq ($(BR2_TOOLCHAIN_EXTERNAL_CODESOURCERY_MIPS201209)$(BR2_TOOLCHAIN_EXTERNAL_CODESOURCERY_MIPS201203),y)
-LIBFFI_CONF_ENV = CFLAGS="$(TARGET_CFLAGS) -mno-compact-eh"
-endif
-
 # Move the headers to the usual location, and adjust the .pc file
 # accordingly.
 define LIBFFI_MOVE_STAGING_HEADERS