Fix building on Xcode

92188d9d1751892ddbf8913da73dfc150d18fadb broke the case where the user
has Xcode but not the command-line tools. So this commit restores
using xcrun to get the path to the SDK (falling back to / for the
non-Xcode case).

http://hydra.nixos.org/build/19953295

Changed files
+4 -4
pkgs
stdenv
darwin
+4 -4
pkgs/stdenv/darwin/default.nix
···
stripAllFlags=" " # the Darwin "strip" command doesn't know "-s"
xargsFlags=" "
export MACOSX_DEPLOYMENT_TARGET=10.7
-
export SDKROOT=
-
export SDKROOT_X=/ # FIXME: impure!
-
export NIX_CFLAGS_COMPILE+=" --sysroot=/var/empty -idirafter $SDKROOT_X/usr/include -F$SDKROOT_X/System/Library/Frameworks -Wno-multichar -Wno-deprecated-declarations"
-
export NIX_LDFLAGS_AFTER+=" -L$SDKROOT_X/usr/lib"
+
# Use the SDK from Xcode by default, falling back to /usr/{lib,include}.
+
export SDKROOT=$(/usr/bin/xcrun --sdk macosx10.9 --show-sdk-path 2> /dev/null || echo /)
+
export NIX_CFLAGS_COMPILE+=" --sysroot=/var/empty -idirafter $SDKROOT/usr/include -F$SDKROOT/System/Library/Frameworks -Wno-multichar -Wno-deprecated-declarations"
+
export NIX_LDFLAGS_AFTER+=" -L$SDKROOT/usr/lib"
export CMAKE_OSX_ARCHITECTURES=x86_64
'';