pkgbase: Fix post-install script for kernel packages

kernel.ucl uses a hardcoded boot/kernel for kldxref, which is the incorrect
directory when we're installing extra kernels that aren't the "default"
kernel (placed at boot/kernel).

Fix this by instead using a new %KERNELDIR% that we now replace in
Makefile.inc1 with "kernel" for the default kernel and "kernel.${_kernel}"
for these extra kernels so that, e.g. /boot/kernel.SHIVA, will get properly
kldxref'd upon update and avoid outdated linker.hints.

Reviewed by:	gjb
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D14689

Makefile.inc1

@@ -1698,6 +1698,7 @@ create-kernel-packages-flavor${flavor:C,^""$,${_default_flavor},}: _pkgbootstrap
 	pwd_arg=`cd ${SRCDIR}/etc ; ${MAKE} -VPWD_MKDB_ENDIAN` ; \
 	sed -e "s/%VERSION%/${PKG_VERSION}/" \
 		-e "s/%PKGNAME%/kernel-${INSTALLKERNEL:tl}${flavor}/" \
+		-e "s/%KERNELDIR%/kernel/" \
 		-e "s/%COMMENT%/FreeBSD ${INSTALLKERNEL} kernel ${flavor}/" \
 		-e "s/%DESC%/FreeBSD ${INSTALLKERNEL} kernel ${flavor}/" \
 		-e "s/%CAP_MKDB_ENDIAN%/$${cap_arg}/g" \
@@ -1733,6 +1734,7 @@ create-kernel-packages-extra-flavor${flavor:C,^""$,${_default_flavor},}-${_kerne
 	pwd_arg=`cd ${SRCDIR}/etc ; ${MAKE} -VPWD_MKDB_ENDIAN` ; \
 	sed -e "s/%VERSION%/${PKG_VERSION}/" \
 		-e "s/%PKGNAME%/kernel-${_kernel:tl}${flavor}/" \
+		-e "s/%KERNELDIR%/kernel.${_kernel}/" \
 		-e "s/%COMMENT%/FreeBSD ${_kernel} kernel ${flavor}/" \
 		-e "s/%DESC%/FreeBSD ${_kernel} kernel ${flavor}/" \
 		-e "s/%CAP_MKDB_ENDIAN%/$${cap_arg}/g" \

release/packages/kernel.ucl

@@ -17,6 +17,6 @@ desc = <<EOD
 EOD
 scripts: {
 	post-install = <<EOD
-	/usr/sbin/kldxref ${PKG_ROOTDIR}/boot/kernel
+	/usr/sbin/kldxref ${PKG_ROOTDIR}/boot/%KERNELDIR%
 EOD
 }