Don't install anything when building as subproject

When a project is consuming unity as as subproject, unity headers,
static library and pkg config files are installed by `meson install`.

This can be fixed by using `meson install --skip-subprojects`, but this
must be repeated in all the distros packaging a project.

Fixed by disabling install when building as a subproject.

Fixes: #661

extras/fixture/src/meson.build

@@ -1,8 +1,10 @@
 unity_inc += include_directories('.')
 unity_src += files('unity_fixture.c')
 
+if not meson.is_subproject()
   install_headers(
     'unity_fixture.h',
     'unity_fixture_internals.h',
     subdir: meson.project_name()
   )
+endif

extras/memory/src/meson.build

@@ -1,7 +1,9 @@
 unity_inc += include_directories('.')
 unity_src += files('unity_memory.c')
 
+if not meson.is_subproject()
   install_headers(
     'unity_memory.h',
     subdir: meson.project_name()
   )
+endif

meson.build

@@ -45,7 +45,7 @@ endif
 unity_lib = static_library(meson.project_name(),
   sources: unity_src,
   include_directories: unity_inc,
-  install: true
+  install: not meson.is_subproject(),
 )
 
 unity_dep = declare_dependency(
@@ -54,6 +54,7 @@ unity_dep = declare_dependency(
 )
 
 # Generate pkg-config file.
+if not meson.is_subproject()
   pkg = import('pkgconfig')
   pkg.generate(
     name: meson.project_name(),
@@ -61,6 +62,7 @@ pkg.generate(
     libraries: [ unity_lib ],
     description: 'C Unit testing framework.'
   )
+endif
 
 # Create a generator that can be used by consumers of our build system to generate
 # test runners.

src/meson.build

@@ -8,8 +8,10 @@
 unity_inc += include_directories('.')
 unity_src += files('unity.c')
 
+if not meson.is_subproject()
   install_headers(
     'unity.h',
     'unity_internals.h',
     subdir: meson.project_name()
   )
+endif