Add MUSL_LDSO_PATHS distro variable

This change adds a post do_install() function that checks if all
subfloders copied from system/lib/module are set in the distro variable
MUSL_LDSO_PATHS and thus are part of the ld-musl-${MUSL_LDSO_ARCH}.path
file.

Signed-off-by: Thierry Escande <thierry.escande@huawei.com>

With this change, the OpenHarmomy lib paths are now added to
/etc/ld-musl-${MUSL_LDSO_ARCH}.path based on the content of the distro
variable MUSL_LDSO_PATHS.

Signed-off-by: Thierry Escande <thierry.escande@huawei.com>

This variable holds the system library folders used by OpenHarmony. It
will be used to generate the file /etc/ld-musl-${MUSL_LDSO_ARCH}.path.
It will also be used to do a sanity check and verify that all
/lib/module/* subfolders are parts of this musl ldso file.

Signed-off-by: Thierry Escande <thierry.escande@huawei.com>