linuxptp: fix do_compile error

with make 4.4, linuxptp do_compile will failed with error:
In file included from clock.c:35:
missing.h:61:9: error: redeclaration of enumerator 'HWTSTAMP_TX_ONESTEP_P2P'
   61 |         HWTSTAMP_TX_ONESTEP_P2P = 3,
      |         ^~~~~~~~~~~~~~~~~~~~~~~
In file included from clock.c:21:
/buildarea2/WRLCD_Regression/Rerun/build_dir/11201532-build_scp_world_Feature_Test/qemux86-64-standard-std-OE/build/tmp-glibc/work/core2-64-wrs-linux/linuxptp/3.1.1-r0/recipe-sysroot/usr/include/linux/net_tstamp.h:128:9: note: previous definition of 'HWTSTAMP_TX_ONESTEP_P2P' with type 'enum hwtstamp_tx_types'
  128 |         HWTSTAMP_TX_ONESTEP_P2P,
      |

Following change of make 4.4 changes behavior of shell function:
* WARNING: Backward-incompatibility!
  Previously makefile variables marked as export were not exported to commands
  started by the $(shell ...) function.  Now, all exported variables are
  exported to $(shell ...).

Signed-off-by: Changqing Li <changqing.li@windriver.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

Backport of commit 05c1003c4 ("linuxptp: fix do_compile error").
This is present in dunfell/kirkstone as well. If net_tstamp.h of the
build host disagrees with net_tstamp.h of the OE kernel or I remove
the build host's net_tstamp.h do_compile fails.

Changed Upstream Status to Backport with the git sha as the commit is
now applied upstream.

Signed-off-by: Max Krummenacher <max.krummenacher@toradex.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>

meta-oe/recipes-connectivity/linuxptp/linuxptp/0001-makefile-use-conditional-assignment-for-KBUILD_OUTPU.patch

@@ -0,0 +1,42 @@
+From dfd38cb29c0768692f886d3ab9158bd2b3132582 Mon Sep 17 00:00:00 2001
+From: Changqing Li <changqing.li@windriver.com>
+Date: Tue, 22 Nov 2022 15:20:48 +0800
+Subject: [PATCH] makefile: use conditional assignment for KBUILD_OUTPUT
+
+Refer [1],from make 4.4, all variables that are marked as export will
+also be passed to the shell started by the shell function. use "=" will
+make KBUILD_OUTPUT always empty for shell function, use "?=" to make
+"export KBUILD_OUTPUT" in enrironment can work.
+
+[snip of 4.4 NEWS]
+* WARNING: Backward-incompatibility!
+   Previously makefile variables marked as export were not exported to commands
+   started by the $(shell ...) function.  Now, all exported variables are
+   exported to $(shell ...).
+[snip]
+
+[1] https://git.savannah.gnu.org/cgit/make.git/tree/NEWS?h=4.4&id=ed493f6c9116cc217b99c2cfa6a95f15803235a2#n74
+
+Upstream-Status: Backport [d3dd51ba611802d7cbb28631cb943cb882fa4aac]
+
+Signed-off-by: Changqing Li <changqing.li@windriver.com>
+---
+ makefile | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/makefile b/makefile
+index 529d8a0..3db60fa 100644
+--- a/makefile
++++ b/makefile
+@@ -15,7 +15,7 @@
+ # with this program; if not, write to the Free Software Foundation, Inc.,
+ # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ 
+-KBUILD_OUTPUT =
++KBUILD_OUTPUT ?=
+ 
+ DEBUG	=
+ CC	?= $(CROSS_COMPILE)gcc
+-- 
+2.25.1
+

meta-oe/recipes-connectivity/linuxptp/linuxptp_2.0.1.bb

@@ -6,6 +6,7 @@ SRC_URI = "http://sourceforge.net/projects/linuxptp/files/v2.0/linuxptp-${PV}.tg
            file://build-Allow-CC-and-prefix-to-be-overriden.patch \
            file://Use-cross-cpp-in-incdefs.patch \
            file://time_t_maybe_long_long.patch \
+           file://0001-makefile-use-conditional-assignment-for-KBUILD_OUTPU.patch \
            "
 
 SRC_URI[sha256sum] = "6f4669db1733747427217a9e74c8b5ca25c4245947463e9cdb860ec8f5ec797a"