package/luasyslog: fix build when host root directory is /usr

Fix the following build failure when host root directory is /usr which
is raised since bump to version 2.2.0 in commit
caa32ac237909999eb6e0bd3616ef4440190970a:

 /usr/bin/install -c -m 644 syslog.lua '/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-0/output-1/target/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-0/output-1/host/usr/share/lua/5.3/logging'
libtool: install: /usr/bin/install -c .libs/lsyslog.so /usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-0/output-1/target/usr/lib/lua/5.3/lsyslog.so
libtool: install: /usr/bin/install -c .libs/lsyslog.lai /usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-0/output-1/target/usr/lib/lua/5.3/lsyslog.la
libtool: warning: remember to run 'libtool --finish /usr/lib/lua/5.3'
/usr/bin/make  install-exec-hook
make[3]: Entering directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-0/output-1/build/luasyslog-2.2.0'
rm -f /usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-0/output-1/target/usr/lib/lua/5.3/lsyslog.la
make[3]: Leaving directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-0/output-1/build/luasyslog-2.2.0'
make[2]: Leaving directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-0/output-1/build/luasyslog-2.2.0'
make[1]: Leaving directory `/usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-0/output-1/build/luasyslog-2.2.0'
luasyslog: installs files in /usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-0/output-1/target//usr/lfs/hdd_v1/rc-buildroot-test/scripts/instance-0/output-1

This failure is raised because lua script directory is "found" and
"fixed" to
${prefix}/lfs/hdd_v1/rc-buildroot-test/scripts/instance-0/output-1/host/usr/share/lua/5.3
because of the following test in ax_lua.m4:

       dnl Try to find a path with the prefix.
        _AX_LUA_FND_PRFX_PTH([$LUA], [$ax_lua_prefix], [package.path])
        AS_IF([test "x$ax_lua_prefixed_path" != 'x'],
        [ dnl Fix the prefix.
          _ax_strip_prefix=`echo "$ax_lua_prefix" | sed 's|.|.|g'`
          ax_cv_lua_luadir=`echo "$ax_lua_prefixed_path" | \
            sed "s,^$_ax_strip_prefix,$LUA_PREFIX,"`
        ])

Fixes:
 - http://autobuild.buildroot.org/results/09fa6dd9844d6d4694801ec59434dad7a56bf290

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/luasyslog/0002-build-ax_lua.m4-fix-cross-compilation.patch

@@ -0,0 +1,45 @@
+From aed16d13d881492e8558f9da21be2dffc4ab2c33 Mon Sep 17 00:00:00 2001
+From: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+Date: Sat, 4 Sep 2021 17:23:58 +0200
+Subject: [PATCH] build/ax_lua.m4: fix cross-compilation
+
+Don't try to "find" and "fix" the script and module directories when
+cross-compiling as this will give unexpected results such as using
+${prefix}/lfs/hdd_v1/rc-buildroot-test/scripts/instance-0/output-1/host/usr/share/lua/5.3
+instead of
+${prefix}/share/lua/5.3
+if the host machine root directory is /usr
+
+Fixes:
+ - http://autobuild.buildroot.org/results/09fa6dd9844d6d4694801ec59434dad7a56bf290
+
+Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+---
+ build/ax_lua.m4 | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/build/ax_lua.m4 b/build/ax_lua.m4
+index 23ca774..7c25cfd 100644
+--- a/build/ax_lua.m4
++++ b/build/ax_lua.m4
+@@ -291,7 +291,7 @@ AC_DEFUN([AX_PROG_LUA],
+ 
+         dnl Try to find a path with the prefix.
+         _AX_LUA_FND_PRFX_PTH([$LUA], [$ax_lua_prefix], [package.path])
+-        AS_IF([test "x$ax_lua_prefixed_path" != 'x'],
++        AS_IF([test "x$ax_lua_prefixed_path" != 'x' && test "x$cross_compiling" != 'xyes'],
+         [ dnl Fix the prefix.
+           _ax_strip_prefix=`echo "$ax_lua_prefix" | sed 's|.|.|g'`
+           ax_cv_lua_luadir=`echo "$ax_lua_prefixed_path" | \
+@@ -318,7 +318,7 @@ AC_DEFUN([AX_PROG_LUA],
+         dnl Try to find a path with the prefix.
+         _AX_LUA_FND_PRFX_PTH([$LUA],
+           [$ax_lua_exec_prefix], [package.cpathd])
+-        AS_IF([test "x$ax_lua_prefixed_path" != 'x'],
++        AS_IF([test "x$ax_lua_prefixed_path" != 'x' && test "x$cross_compiling" != 'xyes'],
+         [ dnl Fix the prefix.
+           _ax_strip_prefix=`echo "$ax_lua_exec_prefix" | sed 's|.|.|g'`
+           ax_cv_lua_luaexecdir=`echo "$ax_lua_prefixed_path" | \
+-- 
+2.32.0
+