build: Minor cleanups

find_program() defaults to require the program in question, and as
failing to locate it is now fatal, there's no longer a need for
checking whether it was found later.

Spotted by Michael Catanzaro.

data/theme/meson.build

@@ -14,14 +14,12 @@ styles = [
 
 theme_deps = []
 
-if sassc.found()
-  foreach style: styles
-    theme_deps += custom_target('style-' + style,
-                                input: '@0@.scss'.format(style),
-                                output: '@0@.css'.format(style),
-                                command: [
-                                  sassc, '-a', '@INPUT@', '@OUTPUT@'
-                                ],
-                                depend_files: theme_sources)
-  endforeach
-endif
+foreach style: styles
+  theme_deps += custom_target('style-' + style,
+                              input: '@0@.scss'.format(style),
+                              output: '@0@.css'.format(style),
+                              command: [
+                                sassc, '-a', '@INPUT@', '@OUTPUT@'
+                              ],
+                              depend_files: theme_sources)
+endforeach

meson.build

@@ -138,7 +138,7 @@ endif
 
 mutter_typelibdir = mutter_dep.get_pkgconfig_variable('typelibdir')
 python = find_program('python3')
-sassc = find_program('sassc', required: true)
+sassc = find_program('sassc')
 
 cc = meson.get_compiler('c')