MDEV-23538: Rename mariadb.pc to mariadbd.pc to avoid confusion

Change so that the client library config can be accessed using the name
libmariadb.pc or mariadb.pc. Rename old mariadb.pc to libmariadbd.pc to
better indicate that the config is for the daemon build, not client.

Adopting the 'lib' naming also better aligns with host most *.pc files
are named.

In downstream Debian we already ship the libmariadb.pc as mariadb.pc:
https://salsa.debian.org/mariadb-team/mariadb-10.5/-/commit/2f183af990fbe1cfa8c343998c7640f45f45368b

After this change we would have for the files:
- libmariadb.pc for client
- libmariadbd.pc for server

debian/libmariadb-dev.install

@@ -30,6 +30,7 @@ usr/lib/*/libmariadbclient.a
 usr/lib/*/libmariadbclient.so
 usr/lib/*/libmysqlservices.a
 usr/lib/*/pkgconfig/libmariadb.pc
+usr/lib/*/pkgconfig/mariadb.pc
 usr/share/aclocal/mysql.m4
 usr/share/man/man1/mariadb_config.1
 usr/share/man/man1/mysql_config.1

debian/libmariadbd-dev.install

@@ -3,4 +3,4 @@ usr/lib/*/libmariadbd.a
 usr/lib/*/libmariadbd.so
 usr/lib/*/libmysqld.a
 usr/lib/*/libmysqld.so
-usr/lib/*/pkgconfig/mariadb.pc
+usr/lib/*/pkgconfig/libmariadbd.pc

debian/rules

@@ -175,6 +175,13 @@ endif
  # Rename and install AppArmor profile
  install -D -m 644 debian/apparmor-profile $(TMP)/etc/apparmor.d/usr.sbin.mariadbd
 
+ # Rename mariadb.pc as libmariadbd.pc as it really is a file for the daemon
+ mv -v $(TMP)/usr/lib/$(DEB_HOST_MULTIARCH)/pkgconfig/mariadb.pc $(TMP)/usr/lib/$(DEB_HOST_MULTIARCH)/pkgconfig/libmariadbd.pc
+
+ # Install mariadb.pc as a symlink for the client library,
+ # use -f to override the existing server mariadb.pc file
+ ln -sf libmariadb.pc $(TMP)/usr/lib/$(DEB_HOST_MULTIARCH)/pkgconfig/mariadb.pc
+
  # Install libmariadbclient18 compatibility links
  ln -s libmariadb.so.3 $(TMP)/usr/lib/$(DEB_HOST_MULTIARCH)/libmariadbclient.so
  ln -s libmariadb.so.3 $(TMP)/usr/lib/$(DEB_HOST_MULTIARCH)/libmariadbclient.so.18