Replace std::experimental::filesystem with ghc::filesystem library.

.gitmodules

@@ -25,3 +25,6 @@
 [submodule "dep/fuzzysearchdatabase"]
 	path = dep/fuzzysearchdatabase
 	url = https://bitbucket.org/j_norberg/fuzzysearchdatabase.git
+[submodule "dep/filesystem"]
+	path = dep/filesystem
+	url = https://github.com/gulrak/filesystem.git

dep/Makefile

@@ -54,6 +54,7 @@ oui-blendish = include/blendish.h
 osdialog = include/osdialog.h
 pffft = include/pffft.h
 fuzzysearchdatabase = include/FuzzySearchDatabase.hpp
+ghcfilesystem = include/ghc/filesystem.hpp
 
 DEPS += $(glew)
 DEPS += $(glfw)
@@ -70,6 +71,7 @@ DEPS += $(oui-blendish)
 DEPS += $(osdialog)
 DEPS += $(pffft)
 DEPS += $(fuzzysearchdatabase)
+DEPS += $(ghcfilesystem)
 
 
 DEP_LOCAL := .
@@ -250,6 +252,10 @@ $(fuzzysearchdatabase): fuzzysearchdatabase/src/FuzzySearchDatabase.hpp
 	mkdir -p include
 	cp $^ include/
 
+$(ghcfilesystem): filesystem/include/ghc
+	mkdir -p include
+	cp -r $^ include/
+
 # Helpers
 
 src: glew-2.1.0 glfw jansson-2.12 speexdsp-SpeexDSP-1.2rc3 openssl-1.1.1d curl-7.66.0 zstd-1.4.5 libarchive-3.4.3 rtmidi-4.0.0 rtaudio nanovg nanosvg oui-blendish osdialog pffft

dep/filesystem

@@ -0,0 +1 @@
+Subproject commit 7e37433f318488ae4bc80f80e12df12a01579874

src/system.cpp

@@ -1,7 +1,7 @@
 #include <thread>
 #include <regex>
 #include <chrono>
-#include <experimental/filesystem>
+#include <ghc/filesystem.hpp>
 
 #include <dirent.h>
 #include <sys/stat.h>
@@ -43,7 +43,7 @@ Important: When using `fs::path`, always convert strings to UTF-8 using
 In fact, it's best to work only with strings to avoid forgetting to decode a string as UTF-8.
 The need to do this is a fatal flaw of `fs::path`, but at least `std::filesystem` has some helpful operations.
 */
-namespace fs = std::experimental::filesystem;
+namespace fs = ghc::filesystem;
 
 
 namespace rack {
@@ -415,7 +415,7 @@ void unarchiveToFolder(const std::string& archivePath, const std::string& folder
 		std::string entryPath = archive_entry_pathname(entry);
 		if (!fs::u8path(entryPath).is_relative())
 			throw Exception(string::f("Unarchiver does not support absolute tar paths: %s", entryPath.c_str()));
-		entryPath = fs::absolute(fs::u8path(entryPath), fs::u8path(folderPath)).generic_u8string();
+		entryPath = fs::relative(fs::u8path(entryPath), fs::u8path(folderPath)).generic_u8string();
 #if defined ARCH_WIN
 		archive_entry_copy_pathname_w(entry, string::U8toU16(entryPath).c_str());
 #else