build.sh: Improve match of linux version sed command

The sed command was matching and changing the spl version number along with the
linux version number. This caused makepkg to fail when building the zfs package
because it was searching for the incorrect spl version number.

build.sh

@@ -135,9 +135,9 @@ update_pkgbuilds() {
     find . -iname "PKGBUILD" -print | xargs sed -i \
         "s/$SED_CUR_ZFS_VER/$ZOL_VERSION/g"
 
-    # Replace the linux version
+    # Replace the linux version, notice "="
     find . -iname "PKGBUILD" -print | xargs sed -i \
-        "s/$SED_CUR_LIN_VER-$CUR_LINUX_PKGREL/$LINUX_VERSION-$LINUX_PKGREL/g"
+        "s/=$SED_CUR_LIN_VER-$CUR_LINUX_PKGREL/=$LINUX_VERSION-$LINUX_PKGREL/g"
 
     # Replace the linux version in the top level VERSION
     find . -iname "PKGBUILD" -print | xargs sed -i \