allow integrating the "make rpm" command into a build system

Allow "make rpm" to take some extra configure options from the build
environment without having to patch the code.

Build the tarball in a temporary directory instead of the e2fsprogs
source directory.

Signed-off-by: Michael MacDonald <Michael.Macdonald@Sun.COM>
Signed-off-by: Andreas Dilger <adilger@sun.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/e2fsprogs.spec.in b/e2fsprogs.spec.in
index 41bf680..51c9b64 100644
--- a/e2fsprogs.spec.in
+++ b/e2fsprogs.spec.in
@@ -62,7 +62,8 @@
 %setup
 
 %build
-%configure --enable-elf-shlibs --enable-nls
+%configure --enable-elf-shlibs --enable-nls \
+	%{?extra_config_flags:%extra_config_flags}
 make
 make check