guix: remove ZERO_AR_DATE export

LLD enables ZERO_AR_DATE by default, setting it to zero would enable
non-determinism, setting it to any other value is ignored.

See:
https://github.com/llvm/llvm-project/blob/main/lld/docs/MachO/ld64-vs-lld.rst.

contrib/guix/libexec/build.sh

@@ -173,16 +173,6 @@ esac
 # Environment variables for determinism
 export TAR_OPTIONS="--owner=0 --group=0 --numeric-owner --mtime='@${SOURCE_DATE_EPOCH}' --sort=name"
 export TZ="UTC"
-case "$HOST" in
-    *darwin*)
-        # cctools AR, unlike GNU binutils AR, does not have a deterministic mode
-        # or a configure flag to enable determinism by default, it only
-        # understands if this env-var is set or not. See:
-        #
-        # https://github.com/tpoechtrager/cctools-port/blob/55562e4073dea0fbfd0b20e0bf69ffe6390c7f97/cctools/ar/archive.c#L334
-        export ZERO_AR_DATE=yes
-        ;;
-esac
 
 ####################
 # Depends Building #

contrib/macdeploy/README.md

@@ -63,9 +63,6 @@ functionality so that a vanilla clang can take advantage. It supports the use of
 `-target`, `-mmacosx-version-min`, and `-isysroot`, which are all necessary when
 building for macOS.
 
-These tools inject timestamps by default, which produce non-deterministic binaries. The
-`ZERO_AR_DATE` environment variable is used to disable that.
-
 To complicate things further, all builds must target an Apple SDK. These SDKs are free to
 download, but not redistributable. See the SDK Extraction notes above for how to obtain it.
 

depends/gen_id

@@ -53,7 +53,6 @@
     echo "BEGIN AR"
     bash -c "${AR} --version"
     env | grep '^AR_'
-    echo "ZERO_AR_DATE=${ZERO_AR_DATE}"
     echo "END AR"
 
     echo "BEGIN NM"