Fix build scripts targeting the wrong architecture

PR bazelbuild#1081 started passing CFLAGS to build scripts, which cargo does
too. But unfortunately Bazel's cpp toolchain adds an explicit target to
the CFLAGS it provides, and that target uses the host platform instead
of the target platform. When building a crate like blake3 or zstd on a
Mac with iOS as the target, this ends up in the crate being built for
macOS instead of iOS.

Author: dae

cargo/cargo_build_script.bzl

@@ -16,8 +16,9 @@ load("//rust/private:utils.bzl", "dedent", "expand_dict_value_locations", "find_
 def strip_target(elems):
     """Remove '-target xxx' from C(XX)FLAGS.
 
-    The cpp toolchain (at least on macOS) adds '-target xxx' to CFLAGS. If it is not stripped out before the CFLAGS are
-    provided to build scripts, it can cause the build to take on the host architecture instead of the target architecture.
+    The cpp toolchain adds '-target xxx' to CFLAGS. If it is not stripped out before the CFLAGS are
+    provided to build scripts, it can cause the build to take on the host architecture instead of the
+    target architecture.
 
     Args:
         elems (list): A list of args