libffi/test: Fix compilation for build sysroot

Fix a problem with the libffi testsuite using a method to determine the
compiler to use resulting in the tool being different from one the
library has been built with, and causing a catastrophic failure from the
inability to actually choose any compiler at all in a cross-compilation
configuration.

Address this problem by providing a DejaGNU configuration file defining
the compiler to use, via the CC_FOR_TARGET TCL variable, set from $CC by
autoconf, which will have all the required options set for the target
compiler to build executables in the environment configured, removing
failures like:

FAIL: libffi.call/closure_fn0.c -W -Wall -Wno-psabi -O0 (test for excess errors)
Excess errors:
default_target_compile: No compiler to compile with
UNRESOLVED: libffi.call/closure_fn0.c -W -Wall -Wno-psabi -O0 compilation failed to produce executable

and bringing overall test results for the `riscv64-linux-gnu' target
(here with the `x86_64-linux-gnu' host and RISC-V QEMU in the Linux user
emulation mode as the target board) from:

		=== libffi Summary ===

# of unexpected failures	708
# of unresolved testcases	708
# of unsupported tests		30

to:

		=== libffi Summary ===

# of expected passes		1934
# of unsupported tests		28

This is a combined backport of the relevant parts of upstream libffi
changes as follows:

- commit 8308984e479e ("[PATCH] Make sure we're running dejagnu tests
  with the right compiler."),

- commit 2d9b3939751b ("[PATCH] Fix for closures with sunpro compiler"),

- commit 0c3824702d3d ("[PATCH] Always set CC_FOR_TARGET for dejagnu, to
  make the testsuite respect $CC"),

- commit 7d698125b1f0 ("[PATCH] Use the proper C++ compiler to run C++
  tests"),

- commit 6b6df1a7bb37 ("[PATCH] Adds `local.exp` to CLEANFILES"),

- commit 6cf0dea78a5a ("[PATCH] Change CLEANFILES to DISTCLEANFILES")

	libffi/
	* Makefile.am (DISTCLEANFILES): New variable.
	* configure.ac: Produce `local.exp'.
	* Makefile.in: Regenerate.
	* configure: Regenerate.
	* testsuite/Makefile.am (EXTRA_DEJAGNU_SITE_CONFIG): New
	variable.
	* testsuite/Makefile.in: Regenerate.

libffi/ChangeLog

@@ -1,3 +1,13 @@
+2020-04-25  Maciej W. Rozycki  <macro@wdc.com>
+
+	* Makefile.am (DISTCLEANFILES): New variable.
+	* configure.ac: Produce `local.exp'.
+	* Makefile.in: Regenerate.
+	* configure: Regenerate.
+	* testsuite/Makefile.am (EXTRA_DEJAGNU_SITE_CONFIG): New
+	variable.
+	* testsuite/Makefile.in: Regenerate.
+
 2020-01-24  Maciej W. Rozycki  <macro@wdc.com>
 
 	* configure.ac: Handle `--with-toolexeclibdir='.

libffi/Makefile.am

@@ -15,6 +15,9 @@ EXTRA_DIST = LICENSE ChangeLog.v1 ChangeLog.libgcj			\
 	libffi.xcodeproj/project.pbxproj				\
 	libtool-ldflags
 
+# local.exp is generated by configure
+DISTCLEANFILES = local.exp
+
 # Automake Documentation:
 # If your package has Texinfo files in many directories, you can use the
 # variable TEXINFO_TEX to tell Automake where to find the canonical

libffi/Makefile.in

@@ -454,6 +454,9 @@ EXTRA_DIST = LICENSE ChangeLog.v1 ChangeLog.libgcj			\
 	libtool-ldflags
 
 
+# local.exp is generated by configure
+DISTCLEANFILES = local.exp
+
 # Automake Documentation:
 # If your package has Texinfo files in many directories, you can use the
 # variable TEXINFO_TEX to tell Automake where to find the canonical
@@ -1674,6 +1677,7 @@ distclean-generic:
 	-rm -f src/x86/$(am__dirstamp)
 	-rm -f src/xtensa/$(DEPDIR)/$(am__dirstamp)
 	-rm -f src/xtensa/$(am__dirstamp)
+	-test -z "$(DISTCLEANFILES)" || rm -f $(DISTCLEANFILES)
 
 maintainer-clean-generic:
 	@echo "This command is intended for maintainers to use"

libffi/configure

@@ -14961,6 +14961,11 @@ _ACEOF
 
 
 
+cat > local.exp <<EOF
+set CC_FOR_TARGET "$CC"
+set CXX_FOR_TARGET "$CXX"
+EOF
+
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to enable maintainer-specific portions of Makefiles" >&5
 $as_echo_n "checking whether to enable maintainer-specific portions of Makefiles... " >&6; }

libffi/configure.ac

@@ -61,6 +61,11 @@ AC_PROG_LIBTOOL
 # Test for 64-bit build.
 AC_CHECK_SIZEOF([size_t])
 
+cat > local.exp <<EOF
+set CC_FOR_TARGET "$CC"
+set CXX_FOR_TARGET "$CXX"
+EOF
+
 AM_MAINTAINER_MODE
 
 AC_CHECK_HEADERS(sys/mman.h)

libffi/testsuite/Makefile.am

@@ -13,6 +13,8 @@ RUNTEST = `if [ -f $(top_srcdir)/../dejagnu/runtest ] ; then \
 
 AM_RUNTESTFLAGS =
 
+EXTRA_DEJAGNU_SITE_CONFIG=../local.exp
+
 CLEANFILES = *.exe core* *.log *.sum
 
 EXTRA_DIST = config/default.exp libffi.call/cls_19byte.c		\

libffi/testsuite/Makefile.in

@@ -279,6 +279,7 @@ RUNTEST = `if [ -f $(top_srcdir)/../dejagnu/runtest ] ; then \
 	       echo $(top_srcdir)/../dejagnu/runtest ; \
 	    else echo runtest; fi`
 
+EXTRA_DEJAGNU_SITE_CONFIG = ../local.exp
 CLEANFILES = *.exe core* *.log *.sum
 EXTRA_DIST = config/default.exp libffi.call/cls_19byte.c		\
 libffi.call/cls_align_longdouble_split.c				\