meson: include the library symbol version list in link_depends

This is pretty ugly, because I don't know how to use a single
definition for two purposes:
- --version-script needs a path relative to the build root
- link_depends needs a path relative to source root
Also, link_depends does not accept files() output
[https://github.com/mesonbuild/meson/issues/1172], and I don't see a way to go
from files() output to a string path that can be used to craft the -Wl arg.

Ideally, a single files() result could be used in both places.
I'm leaving this as a separate commit for now.

src/libsystemd/meson.build

@@ -88,7 +88,7 @@ libsystemd_internal = static_library(
     dependencies : [threads,
                     librt])
 
-libsystemd_sym = meson.current_source_dir() + '/libsystemd.sym'
+libsystemd_sym = 'src/libsystemd/libsystemd.sym'
 
 libsystemd_pc = configure_file(
     input : 'libsystemd.pc.in',

src/libudev/meson.build

@@ -16,17 +16,19 @@ libudev_sources = '''
 
 ############################################################
 
-libudev_sym = meson.current_source_dir() + '/libudev.sym'
+libudev_sym = 'libudev.sym'
 
+version_script_arg = '@0@/@1@'.format(meson.current_source_dir(), libudev_sym)
 libudev = shared_library(
     'udev',
     libudev_sources,
     version : '1.6.6',
     include_directories : includes,
     link_args : ['-shared',
-                 '-Wl,--version-script=' + libudev_sym],
+                 '-Wl,--version-script=' + version_script_arg],
     link_with : [libbasic,
                  libsystemd],
+    link_depends : libudev_sym,
     install : true,
     install_dir : rootlibdir)
 

src/login/meson.build

@@ -65,7 +65,7 @@ if conf.get('ENABLE_LOGIND', 0) == 1
   install_data(logind_conf,
                install_dir : pkgsysconfdir)
 
-  pam_systemd_sym = meson.current_source_dir() + '/pam_systemd.sym'
+  pam_systemd_sym = 'src/login/pam_systemd.sym'
   pam_systemd_c = files('pam_systemd.c')
 
   install_data('org.freedesktop.login1.conf',