macOS: optionally make a generically-named copy of the zip (#6518)

Adds `-DOSX_NIGHTLY`. With -DOSX_NIGHTLY=ON will produce copies of the zip with generic names: `RawTherapee_macOS_arm64_latest.zip` for the purpose of hyperlinking. This is activated for GitHub Actions automated builds.

* mac: specify catalina on github action
* mac: use clang instead of /path/to/clang
* mac: Exec Architectures --> Architecture Priority
* mac: add an option to generate a universal app
* mac: generate a universal app
* mac: use "Universal" for arch in naming
* mac: remove some braces
* mac: fix gtk3 environment paths
* mac: fix universal url logic
* mac: merge about txts for universal build
* Mac: fix osx version minimums in universal 1
* Mac: update info plist for osx version minima
* Mac: update universal versioning
* Mac: add processor tunings for sandy-ivy bridge
* mac: fix minimum versioning statements
* Mac: fix a paste error
* mac: remove any x/X libs from bundle
* mac: don't get rid of libxcb for cairo
* mac: fix a typo
* mac: revert library removals for cairo

tools/osx/Info.plist.in

@@ -3,10 +3,14 @@
     <dict>
         <key>LSEnvironment</key>
         <dict>
-            <key>XDG_DATA_DIRS</key>
+            <key>XDG_CONFIG_DIRS</key>
+            <string>/Applications/RawTherapee.app/Contents/Resources/share/gtk-3.0</string>
+            <key>XDG_CONFIG_HOME</key>
             <string>/Applications/RawTherapee.app/Contents/Resources/share</string>
+            <key>XDG_DATA_DIRS</key>
+            <string>/Applications/RawTherapee.app/Contents/Resources/share/gtk-3.0</string>
             <key>GTK_PATH</key>
-            <string>/Applications/RawTherapee.app/Contents/Frameworks</string>
+            <string>/Applications/RawTherapee.app/Contents/Resources/share/gtk-3.0</string>
             <key>GTK_IM_MODULE_FILE</key>
             <string>/Applications/RawTherapee.app/Contents/Resources/etc/gtk-3.0/gtk.immodules</string>
             <key>XDG_DATA_HOME</key>
@@ -28,8 +32,13 @@
         </dict>
         <key>LSMultipleInstancesProhibited</key>
         <true />
-        <key>LSMinimumSystemVersion</key>
-        <string>@minimum_macos_version@</string>
+        <key>LSMinimumSystemVersionByArchitecture</key>
+        <dict>
+            <key>arm64</key>
+            <string>@minimum_arm64_version@</string>
+            <key>x86_64</key>
+            <string>@minimum_x86_64_version@</string>
+        </dict>
         <key>CFBundleAllowMixedLocalizations</key>
         <true />
         <key>CFBundleDisplayName</key>
@@ -156,9 +165,10 @@
         <string>????</string>
         <key>CFBundleVersion</key>
         <string>@shortVersion@</string>
-        <key>LSExecutableArchitectures</key>
+        <key>LSArchitecturePriority</key>
         <array>
-            <string>@arch@</string>
+            <string>arm64</string>
+            <string>x86_64</string>
         </array>
         <key>NSHighResolutionCapable</key>
         <true />