rename: build-utils-meson -> nix-meson-build-support

Fix a footgun. In my case, I had a couple of build ("output")
directories sitting around.

    rm -rf build-*

Was confused for a bit why a meson.build file was missing.

Probably also helps with autocompletion.

I tried meson-build-support first, but I had to add something like
a nix- prefix, in order to make meson happy. They've reserved the
meson- prefix.

src/libutil/build-utils-meson

@@ -1 +0,0 @@
-../../build-utils-meson

src/libutil/meson.build

@@ -14,7 +14,7 @@ project('nix-util', 'cpp',
 
 cxx = meson.get_compiler('cpp')
 
-subdir('build-utils-meson/deps-lists')
+subdir('nix-meson-build-support/deps-lists')
 
 configdata = configuration_data()
 
@@ -22,7 +22,7 @@ deps_private_maybe_subproject = [
 ]
 deps_public_maybe_subproject = [
 ]
-subdir('build-utils-meson/subprojects')
+subdir('nix-meson-build-support/subprojects')
 
 # Check for each of these functions, and create a define like `#define
 # HAVE_LUTIMES 1`. The `#define` is unconditional, 0 for not found and 1
@@ -53,7 +53,7 @@ endforeach
 
 configdata.set('HAVE_DECL_AT_SYMLINK_NOFOLLOW', cxx.has_header_symbol('fcntl.h', 'AT_SYMLINK_NOFOLLOW').to_int())
 
-subdir('build-utils-meson/libatomic')
+subdir('nix-meson-build-support/libatomic')
 
 if host_machine.system() == 'windows'
   socket = cxx.find_library('ws2_32')
@@ -120,7 +120,7 @@ add_project_arguments(
   language : 'cpp',
 )
 
-subdir('build-utils-meson/common')
+subdir('nix-meson-build-support/common')
 
 sources = files(
   'archive.cc',
@@ -256,8 +256,8 @@ else
   subdir('unix')
 endif
 
-subdir('build-utils-meson/export-all-symbols')
-subdir('build-utils-meson/windows-version')
+subdir('nix-meson-build-support/export-all-symbols')
+subdir('nix-meson-build-support/windows-version')
 
 this_library = library(
   'nixutil',
@@ -278,4 +278,4 @@ if host_machine.system() == 'windows'
   libraries_private += ['-lws2_32']
 endif
 
-subdir('build-utils-meson/export')
+subdir('nix-meson-build-support/export')

src/libutil/nix-meson-build-support

@@ -0,0 +1 @@
+../../nix-meson-build-support

src/libutil/package.nix

@@ -25,8 +25,8 @@ mkMesonLibrary (finalAttrs: {
 
   workDir = ./.;
   fileset = fileset.unions [
-    ../../build-utils-meson
-    ./build-utils-meson
+    ../../nix-meson-build-support
+    ./nix-meson-build-support
     ../../.version
     ./.version
     ./meson.build