kpatch-build: introduce ability to ignore distro-specific checks

Ignore distro-specific checks if kernel source directory is supplied as a
command line argument to remove the distro-specific tunings during
cross-compilation.

Signed-off-by: Ruslan Bilovol <rbilovol@cisco.com>
Signed-off-by: Oleh Matiusha <oleh.matiusha@globallogic.com>

Author: omatiusha

kpatch-build/kpatch-build

@@ -705,8 +705,11 @@ fi
 
 # Don't check external file.
 # shellcheck disable=SC1090
-[[ -f "$RELEASE_FILE" ]] && source "$RELEASE_FILE"
-DISTRO="$ID"
+if [[ -z "$USERSRCDIR" ]] && [[ -f "$RELEASE_FILE" ]]; then
+	source "$RELEASE_FILE"
+	DISTRO="$ID"
+fi
+
 if [[ "$DISTRO" = fedora ]] || [[ "$DISTRO" = rhel ]] || [[ "$DISTRO" = ol ]] || [[ "$DISTRO" = centos ]] || [[ "$DISTRO" = openEuler ]]; then
 	[[ -z "$VMLINUX" ]] && VMLINUX="/usr/lib/debug/lib/modules/$ARCHVERSION/vmlinux"
 	[[ -e "$VMLINUX" ]] || die "kernel-debuginfo-$ARCHVERSION not installed"