btrfs-progs: makefile: add support for additional build flags

Allow fine tuned build options via EXTRA_CFLAGS and EXTRA_LDFLAGS
variables. Useful for additional debugging flags or warnings etc.

Signed-off-by: David Sterba <dsterba@suse.com>

INSTALL

@@ -42,7 +42,11 @@ Specific CFLAGS or LDFLAGS should be set like
 
  $ CFLAGS=... LDFLAGS=... ./configure --prefix=/usr
 
-and not as arguments to make.
+and not as arguments to make. You can specify additional flags to build via
+variables EXTRA_CFLAGS and EXTRA_LDFLAGS that get appended to the predefined
+values of the respective variables.
+
+ $ make EXTRA_CFLAGS=-ggdb3
 
 References:
 * https://btrfs.wiki.kernel.org

Makefile.in

@@ -10,16 +10,19 @@ INSTALL = @INSTALL@
 DISABLE_DOCUMENTATION = @DISABLE_DOCUMENTATION@
 DISABLE_BTRFSCONVERT = @DISABLE_BTRFSCONVERT@
 
+EXTRA_CFLAGS :=
+EXTRA_LDFLAGS :=
+
 # Common build flags
 CFLAGS = @CFLAGS@ \
 	 -include config.h \
 	 -DBTRFS_FLAT_INCLUDES \
 	 -D_XOPEN_SOURCE=700  \
 	 -fno-strict-aliasing \
-	 -fPIC
+	 -fPIC $(EXTRA_CFLAGS)
 
 LDFLAGS = @LDFLAGS@ \
-	  -rdynamic
+	  -rdynamic $(EXTRA_LDFLAGS)
 
 LIBS = @UUID_LIBS@ @BLKID_LIBS@ @ZLIB_LIBS@ @LZO2_LIBS@ -L. -pthread
 LIBBTRFS_LIBS = $(LIBS)