[vte] build: Don't install test app when building as subproject

[Christian Persch <chpe src gnome org>]

commit 7044294b737b92a4afb15cfeb64ae09053cb85c1
Author: Christian Persch <chpe src gnome org>
Date:   Sat Apr 3 16:07:50 2021 +0200

    build: Don't install test app when building as subproject

 src/app/meson.build | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/app/meson.build b/src/app/meson.build
index dd9c713c..e719d9f0 100644
--- a/src/app/meson.build
+++ b/src/app/meson.build
@@ -53,7 +53,7 @@ if get_option('gtk3')
     dependencies: app_gtk3_deps,
     cpp_args: app_gtk3_cppflags,
     include_directories: top_inc,
-    install: true,
+    install: not meson.is_subproject(),
   )
 endif
 
@@ -82,6 +82,6 @@ if get_option('gtk4')
     dependencies: app_gtk4_deps,
     cpp_args: app_gtk4_cppflags,
     include_directories: top_inc,
-    install: true,
+    install: not meson.is_subproject(),
   )
 endif