[PATCH v2 1/4] doc: arm64 cross build CFLAGS/LDFLAGS alternatives

["Juraj Linkeš" <juraj.linkes@pantheon.tech>]

Remove CFLAGS and LDFLAGS since Meson doesn't support them well enough.
Add Meson alternatives: -Dc_args and -Dc_link_args on the command line
and in cross files.

Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
---
 .../linux_gsg/cross_build_dpdk_for_arm64.rst  | 25 ++++++++++++++++---
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/doc/guides/linux_gsg/cross_build_dpdk_for_arm64.rst b/doc/guides/linux_gsg/cross_build_dpdk_for_arm64.rst
index d59af58235..51075bd4a9 100644
--- a/doc/guides/linux_gsg/cross_build_dpdk_for_arm64.rst
+++ b/doc/guides/linux_gsg/cross_build_dpdk_for_arm64.rst
@@ -98,10 +98,6 @@ For aarch32::
 Augment the GNU toolchain with NUMA support
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-.. note::
-
-   This way is optional, an alternative is to use extra CFLAGS and LDFLAGS.
-
 Copy the NUMA header files and lib to the cross compiler's directories:
 
 .. code-block:: console
@@ -110,6 +106,27 @@ Copy the NUMA header files and lib to the cross compiler's directories:
    cp <numa_install_dir>/lib/libnuma.a <cross_install_dir>/gcc-arm-9.2-2019.12-x86_64-aarch64-none-linux-gnu/lib/gcc/aarch64-none-linux-gnu/9.2.1/
    cp <numa_install_dir>/lib/libnuma.so <cross_install_dir>/gcc-arm-9.2-2019.12-x86_64-aarch64-none-linux-gnu/lib/gcc/aarch64-none-linux-gnu/9.2.1/
 
+.. note::
+
+   Using LDFLAGS and CFLAGS is not a viable alternative to copying the files.
+   The Meson docs say it is not recommended, as there are many caveats to their
+   use with Meson, especially when rebuilding the project. A viable alternative
+   would be to use the ``c_args`` and ``c_link_args`` options with Meson 0.51.0
+   and higher:
+
+.. code-block:: console
+
+   -Dc_args=-I<numa_install_dir>/include -Dc_link_args=-L<numa_install_dir>/lib
+
+   For Meson versions lower than 0.51.0, the ``c_args`` and ``c_link_args``
+   options don't apply to cross compilation. However, the compiler/linker flags
+   may be added to cross files under [properties]:
+
+.. code-block:: console
+
+   c_args = ['-I<numa_install_dir>/include']
+   c_link_args = ['-L<numa_install_dir>/lib']
+
 Cross Compiling DPDK with GNU toolchain using Meson
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-- 
2.20.1