build: sanity check options

Fail when tests/documentation is enabled without libraries. Fail
when neither scanner nor libraries is enabled, because we don't
build anything in that case.

Signed-off-by: Simon Ser <contact@emersion.fr>

doc/meson.build

@@ -1,3 +1,7 @@
+if not get_option('libraries')
+	error('-Ddocumentation=true requires -Dlibraries=true')
+endif
+
 dot = find_program('dot')
 doxygen = find_program('doxygen')
 xsltproc = find_program('xsltproc')

meson.build

@@ -118,12 +118,12 @@ subdir('src')
 if get_option('libraries')
 	subdir('cursor')
 	subdir('egl')
-	if get_option('tests')
-		subdir('tests')
-	endif
-	if get_option('documentation')
-		subdir('doc')
-	endif
+endif
+if get_option('tests')
+	subdir('tests')
+endif
+if get_option('documentation')
+	subdir('doc')
 endif
 
 if get_option('scanner')

src/meson.build

@@ -1,3 +1,7 @@
+if not (get_option('scanner') or get_option('libraries'))
+	error('Either -Dscanner=true or -Dlibraries=true is required')
+endif
+
 wayland_version_h = configuration_data()
 wayland_version_h.set('WAYLAND_VERSION', meson.project_version())
 wayland_version_h.set('WAYLAND_VERSION_MAJOR', wayland_version[0].to_int())

tests/meson.build

@@ -1,3 +1,7 @@
+if not get_option('libraries')
+	error('-Dtests=true requires -Dlibraries=true')
+endif
+
 test_runner = static_library(
 	'test-runner',
 	sources: [