folly: split outputs to reduce closure sizes

This shaves off a 100MiB+ `boost.dev` dependence from `folly.out`, which
would benefit all downstream packages that dynamically link to folly.

Upstream's cmake configuration is not suitable for split packages, and
some tweaks are applied for it to work; these are taken from:

- 04384d5
- 8d712cc

See: https://github.com/jtojnar/cmake-snips

pkgs/development/libraries/folly/default.nix

@@ -4,7 +4,6 @@
 , boost
 , cmake
 , double-conversion
-, fetchpatch
 , fmt_8
 , gflags
 , glog
@@ -64,12 +63,21 @@ stdenv.mkDerivation rec {
     # temporary hack until folly builds work on aarch64,
     # see https://github.com/facebook/folly/issues/1880
     "-DCMAKE_LIBRARY_ARCHITECTURE=${if stdenv.isx86_64 then "x86_64" else "dummy"}"
+
+    # ensure correct dirs in $dev/lib/pkgconfig/libfolly.pc
+    # see https://github.com/NixOS/nixpkgs/issues/144170
+    "-DCMAKE_INSTALL_INCLUDEDIR=include"
+    "-DCMAKE_INSTALL_LIBDIR=lib"
   ];
 
+  # split outputs to reduce downstream closure sizes
+  outputs = [ "out" "dev" ];
+
+  # patch prefix issues again
+  # see https://github.com/NixOS/nixpkgs/issues/144170
   postFixup = ''
-    substituteInPlace "$out"/lib/pkgconfig/libfolly.pc \
-      --replace '=''${prefix}//' '=/' \
-      --replace '=''${exec_prefix}//' '=/'
+    substituteInPlace $dev/lib/cmake/${pname}/${pname}-targets-release.cmake  \
+      --replace '$'{_IMPORT_PREFIX}/lib/ $out/lib/
   '';
 
   # folly-config.cmake, will `find_package` these, thus there should be