Meson: Replace option `instlibdir` with `libexecdir`

Derive a value from it, called `rundir` rather than writing join_paths(libexecdir,
'sway') all over the place.

meson.build

@@ -19,12 +19,13 @@ is_freebsd = host_machine.system().startswith('freebsd')
 datadir = get_option('datadir')
 sysconfdir = get_option('sysconfdir')
 prefix = get_option('prefix')
-instlibdir = get_option('instlibdir')
+libexecdir = get_option('libexecdir')
 
-if instlibdir == ''
-  instlibdir = join_paths(prefix, 'lib/sway')
+if libexecdir == ''
+	libexecdir = 'lib'
 endif
-add_project_arguments('-DINSTLIBDIR="/@0@"'.format(instlibdir), language : 'c')
+sway_libexecdir = join_paths(prefix, libexecdir, 'sway')
+add_project_arguments('-DSWAY_LIBEXECDIR="/@0@"'.format(sway_libexecdir), language : 'c')
 
 
 jsonc          = dependency('json-c', version: '>=0.13')

meson_options.txt

@@ -1,4 +1,3 @@
-option('instlibdir', type: 'string', description: 'Installation path for sway-internal executables, such as swaybg or swaybar.  (Default: prefix/lib/sway)')
 option('sway_version', type : 'string', description: 'The version string reported in `sway --version`.')
 option('default_wallpaper', type: 'boolean', value: true, description: 'Install the default wallpaper.')
 option('zsh_completions', type: 'boolean', value: true, description: 'Install zsh shell completions.')

sway/commands/exec_always.c

@@ -55,8 +55,8 @@ struct cmd_results *cmd_exec_always(int argc, char **argv) {
 		if ((*child = fork()) == 0) {
 			// Acquire the current PATH
 			char *path = getenv("PATH");
-			const char *extra_path = ":" INSTLIBDIR;
-			const size_t extra_size = sizeof(INSTLIBDIR) + 1;
+			const char *extra_path = ":" SWAY_LIBEXECDIR;
+			const size_t extra_size = sizeof(SWAY_LIBEXECDIR) + 1;
 
 			if (!path) {
 				size_t n = confstr(_CS_PATH, NULL, 0);

swaybar/meson.build

@@ -25,5 +25,5 @@ executable(
 	],
 	link_with: [lib_sway_common, lib_sway_client],
 	install: true,
-	install_dir: instlibdir
+	install_dir: sway_libexecdir
 )

swaybg/meson.build

@@ -15,5 +15,5 @@ executable(
 	],
 	link_with: [lib_sway_common, lib_sway_client],
 	install: true,
-	install_dir: instlibdir
+	install_dir: sway_libexecdir
 )