[PATCH] btrfs-progs: fix cross-compile build

[Eric Sandeen <sandeen@redhat.com>]

The mktables binary needs to be build with the host
compiler at built time, not the target compiler, because
it runs at build time to generate the raid tables.

Copy auto-fu from xfsprogs and modify Makefile to
accomodate this.

Reported-by: Hallo32 <Hallo32@gmx.net>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

diff --git a/Makefile b/Makefile
index b3e2b63..2647b95 100644
--- a/Makefile
+++ b/Makefile
@@ -323,7 +323,7 @@ version.h: version.sh version.h.in configure.ac
 
 mktables: kernel-lib/mktables.c
 	@echo "    [CC]     $@"
-	$(Q)$(CC) $(CFLAGS) $< -o $@
+	$(Q)$(BUILD_CC) $(BUILD_CFLAGS) $< -o $@
 
 kernel-lib/tables.c: mktables
 	@echo "    [TABLE]  $@"
diff --git a/Makefile.inc.in b/Makefile.inc.in
index 4e1b68c..0570bf8 100644
--- a/Makefile.inc.in
+++ b/Makefile.inc.in
@@ -4,6 +4,8 @@
 export
 
 CC = @CC@
+BUILD_CC = @BUILD_CC@
+BUILD_CFLAGS = @BUILD_CFLAGS@
 LN_S = @LN_S@
 AR = @AR@
 RM = @RM@
diff --git a/configure.ac b/configure.ac
index 30055f8..bc590cc 100644
--- a/configure.ac
+++ b/configure.ac
@@ -26,6 +26,23 @@ AC_CONFIG_SRCDIR([btrfs.c])
 AC_PREFIX_DEFAULT([/usr/local])
 
 AC_PROG_CC
+AC_ARG_VAR(BUILD_CC, [C compiler for build tools])
+if test "${BUILD_CC+set}" != "set"; then
+  if test $cross_compiling = no; then
+    BUILD_CC="$CC"
+  else
+    AC_CHECK_PROGS(BUILD_CC, gcc cc)
+  fi
+fi
+AC_ARG_VAR(BUILD_CFLAGS, [C compiler flags for build tools])
+if test "${BUILD_CFLAGS+set}" != "set"; then
+  if test $cross_compiling = no; then
+    BUILD_CFLAGS="$CFLAGS"
+  else
+    BUILD_CFLAGS="-g -O2"
+  fi
+fi
+
 AC_CANONICAL_HOST
 AC_C_CONST
 AC_C_VOLATILE