Add a Meson wrap for ghc::filesystem

Which can replace Boost.Filesystem for us so we can get rid of the
runtime dependency.

CHANGELOG.md

@@ -20,6 +20,9 @@ Versioning](https://semver.org/spec/v2.0.0.html).
 
 ### Packaging notes
 
+- Added a dependency on the headers-only
+  [`ghc::filesystem`](https://github.com/gulrak/filesystem) library to replace
+  Boost.Filesystem.
 - Fixed a deprecation warning in the Meson build, causing the minimum supported
   Meson version to be bumped up to **Meson 0.56** from 0.55.
 

subprojects/.gitignore

@@ -3,10 +3,12 @@
 # The above pattern doesn't match submodules
 /bitsery
 /function2
+/ghc_filesystem
 /tomlplusplus
 /vst3
 
 # And we obviously don't want to ignore our overlays
 !/packagefiles/bitsery
 !/packagefiles/function2
+!/packagefiles/ghc_filesystem
 !/function2-patch/*

subprojects/ghc_filesystem.wrap

@@ -0,0 +1,9 @@
+[wrap-git]
+url = https://github.com/gulrak/filesystem.git
+# This is tag v1.5.12
+revision = cd6805e94dd5d6346be1b75a54cdc27787319dd2
+depth = 1
+patch_directory = ghc_filesystem
+
+[provide]
+ghc_filesystem = ghc_filesystem_dep

subprojects/packagefiles/ghc_filesystem/meson.build

@@ -0,0 +1,3 @@
+project('ghc_filesystem', 'cpp', version : '1.5.2')
+
+ghc_filesystem_dep = declare_dependency(include_directories : include_directories('include'))