Enable --version-sort on systems without strverscmp()

The --version-sort option requires strverscmp(), but this is a glibc
extension that does not exist on OpenBSD and other systems. To enable
--version-sort on those systems, provide an internal implementation of
strverscmp(). The implementation is from the musl C library and is
MIT-licensed.

The build process remains the same: the verscmp flag should be set to 1
only if strverscmp() is available in libc. If verscmp is 0, then the
internal implementation is used.

1 files changed, 4 insertions, 0 deletions

diff --git a/src/Makefile b/src/Makefile
index ac4d2fe..10e33eb 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -34,6 +34,10 @@ ifeq (${exif},1)
 		exif_nikon.c
 endif
 
+ifneq (${verscmp},1)
+	TARGETS += strverscmp.c
+endif
+
 OBJECTS = ${TARGETS:.c=.o}
 
 I_SRCS = ${shell echo *.raw}