config/zfs-build.m4: add --with-vendor flag

This will allow an override of auto-detection of distribution, which
is based on checking presence of /etc/*-release files.

Build systems makes a lot of file location assumptions based on
detected distribution.

Some distributions (like gentoo) may prefer explicitly
setting --with-vendor=gentoo to avoid auto-detection.

Since auto-detection checks all files in order, current script may
misdetect even on gentoo system if /etc/redhat-release file is present

Default behavior is unchanged and default is --with-vendor=check

Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Georgy Yakovlev <gyakovlev@gentoo.org>
Closes #10835

config/zfs-build.m4

@@ -418,33 +418,43 @@ dnl # package type for 'make pkg': (rpm | deb | tgz)
 dnl #
 AC_DEFUN([ZFS_AC_DEFAULT_PACKAGE], [
 	AC_MSG_CHECKING([os distribution])
-	if test -f /etc/toss-release ; then
-		VENDOR=toss ;
-	elif test -f /etc/fedora-release ; then
-		VENDOR=fedora ;
-	elif test -f /etc/redhat-release ; then
-		VENDOR=redhat ;
-	elif test -f /etc/gentoo-release ; then
-		VENDOR=gentoo ;
-	elif test -f /etc/arch-release ; then
-		VENDOR=arch ;
-	elif test -f /etc/SuSE-release ; then
-		VENDOR=sles ;
-	elif test -f /etc/slackware-version ; then
-		VENDOR=slackware ;
-	elif test -f /etc/lunar.release ; then
-		VENDOR=lunar ;
-	elif test -f /etc/lsb-release ; then
-		VENDOR=ubuntu ;
-	elif test -f /etc/debian_version ; then
-		VENDOR=debian ;
-	elif test -f /etc/alpine-release ; then
-		VENDOR=alpine ;
-	elif test -f /bin/freebsd-version ; then
-		VENDOR=freebsd ;
-	else
-		VENDOR= ;
-	fi
+	AC_ARG_WITH([vendor],
+		[AS_HELP_STRING([--with-vendor],
+			[Distribution vendor @<:@default=check@:>@])],
+		[with_vendor=$withval],
+		[with_vendor=check])
+	AS_IF([test "x$with_vendor" = "xcheck"],[
+		if test -f /etc/toss-release ; then
+			VENDOR=toss ;
+		elif test -f /etc/fedora-release ; then
+			VENDOR=fedora ;
+		elif test -f /etc/redhat-release ; then
+			VENDOR=redhat ;
+		elif test -f /etc/gentoo-release ; then
+			VENDOR=gentoo ;
+		elif test -f /etc/arch-release ; then
+			VENDOR=arch ;
+		elif test -f /etc/SuSE-release ; then
+			VENDOR=sles ;
+		elif test -f /etc/slackware-version ; then
+			VENDOR=slackware ;
+		elif test -f /etc/lunar.release ; then
+			VENDOR=lunar ;
+		elif test -f /etc/lsb-release ; then
+			VENDOR=ubuntu ;
+		elif test -f /etc/debian_version ; then
+			VENDOR=debian ;
+		elif test -f /etc/alpine-release ; then
+			VENDOR=alpine ;
+		elif test -f /bin/freebsd-version ; then
+			VENDOR=freebsd ;
+		else
+			VENDOR= ;
+		fi],
+		[ test "x${with_vendor}" != x],[
+			VENDOR="$with_vendor" ],
+		[ VENDOR= ; ]
+	)
 	AC_MSG_RESULT([$VENDOR])
 	AC_SUBST(VENDOR)