btrfsProgs: Cleanup some old build changes

The change of optimization flags should be safe for all platforms as
the default for most applications is -O2. It is also unecessary to
forcefully link against libgcc_s as btrfsprogs no longer errors when
scrubbing without this linkage.

pkgs/tools/filesystems/btrfsprogs/default.nix

@@ -1,9 +1,10 @@
 { stdenv, fetchurl, pkgconfig, attr, acl, zlib, libuuid, e2fsprogs, lzo
-, asciidoc, xmlto, docbook_xml_dtd_45, docbook_xsl, libxslt }:
+, asciidoc, xmlto, docbook_xml_dtd_45, docbook_xsl, libxslt
+}:
 
 let version = "4.1.1"; in
 
-stdenv.mkDerivation (rec {
+stdenv.mkDerivation rec {
   name = "btrfs-progs-${version}";
 
   src = fetchurl {
@@ -16,10 +17,9 @@ stdenv.mkDerivation (rec {
     asciidoc xmlto docbook_xml_dtd_45 docbook_xsl libxslt
   ];
 
-  # for btrfs to get the rpath to libgcc_s, needed for pthread_cancel to work
-  NIX_CFLAGS_LINK = "-lgcc_s";
-
-  makeFlags = "prefix=$(out)";
+  # gcc bug with -O1 on ARM with gcc 4.8
+  # This should be fine on all platforms so apply universally
+  patchPhase = "sed -i s/-O1/-O2/ configure";
 
   meta = with stdenv.lib; {
     description = "Utilities for the btrfs filesystem";
@@ -28,7 +28,4 @@ stdenv.mkDerivation (rec {
     maintainers = with maintainers; [ raskin wkennington ];
     platforms = platforms.linux;
   };
-} // (if stdenv.isArm then {
-  # gcc bug with -O1 on ARM
-  patchPhase = "sed -i s/-O1/-O2/ configure";
-} else {}))
+}