bintools-wrapper: default platform versions for darwin

Instead of always supplying flags, apply the flags as defaults. Use
clang's native flags instead of lifting the linker flags from binutils
with `-Wl,`.

If a project is using clang to drive linking, make clang do the right
thing with MACOSX_DEPLOYMENT_TARGET. This can be overridden by command
line arguments. This will cause modern clang to pass
`-platform_version 10.12 0.0.0`, since it doesn't know about the SDK
settings. Older versions of clang will pass down `-macos_version_min`
flags with no sdk version.

At the linker layer, apply a default value for anything left
ambiguous. If nothing is specified, pass a full
`-platform_version`. If only `-macos_version_min` is specified, then
lock down the sdk_version explicitly with `-sdk_version`. If a min
version and sdk version is passed, do nothing.

1 files changed, 8 insertions, 0 deletions

diff --git a/pkgs/build-support/bintools-wrapper/ld-wrapper.sh b/pkgs/build-support/bintools-wrapper/ld-wrapper.sh
index 9d02f99851a57..7ccf5510c8808 100644
--- a/pkgs/build-support/bintools-wrapper/ld-wrapper.sh
+++ b/pkgs/build-support/bintools-wrapper/ld-wrapper.sh
@@ -78,6 +78,14 @@ fi
 
 extraAfter+=($NIX_LDFLAGS_AFTER_@suffixSalt@)
 
+# These flags *must not* be pulled up to -Wl, flags, so they can't go in
+# add-flags.sh. They must always be set, so must not be disabled by
+# NIX_LDFLAGS_SET.
+if [ -e @out@/nix-support/add-local-ldflags-before.sh ]; then
+    source @out@/nix-support/add-local-ldflags-before.sh
+fi
+
+
 # Specify the target emulation if nothing is passed in ("-m" overrides this
 # environment variable). Ensures we never blindly fallback on targeting the host
 # platform.