This reduces code duplication, makes the SDK variables available
earlier in the wrappers, and makes the behaviour between the two
wrappers more consistent.
This is basically harmless for the same reason as it is for Clang, and
lets us avoid doing wrapper hacks to fix things like the .NET build.
This reverts commit 4340a5addb.
It is unusual to invoke a wrapped compiler without setting
`DEVELOPER_DIR`, but it can happen when a user adds a compiler to their
installed packages or when a package intentionally invokes the compiler
without an environment (such as the GHC binary packages).
Some compilers may know to check these paths when `SDKROOT` is set, but
it’s not assumed they do. `SDKROOT` is instead derived from the
`DEVELOPER_DIR`, and `NIX_CFLAGS_COMPILE` is set up with the sysroot and
necessary framework and include search paths.
In a typical build environment the toolchain will use the value of the
MACOSX_DEPLOYMENT_TARGET environment variable to determine the version
of macOS to support. When cross compiling there are two distinct
toolchains, but they will look at this single environment variable. To
avoid contamination, we always set the equivalent command line flag
which effectively disables the toolchain's internal handling.
Prior to this change, the MACOSX_DEPLOYMENT_TARGET variable was
ignored, and the toolchains always used the Nix platform
definition (`darwinMinVersion`) unless overridden with command line
arguments.
This change restores support for MACOSX_DEPLOYMENT_TARGET, and adds
nix-specific MACOSX_DEPLOYMENT_TARGET_FOR_BUILD and
MACOSX_DEPLOYMENT_TARGET_FOR_TARGET for cross compilation.
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.
