perl: complete reproducibility — pin all host/time-derived Config fields

packages/perl/build.sh

@@ -15,10 +15,27 @@ export CFLAGS="$MARCH -O2 -pipe -gno-record-gcc-switches -ffile-prefix-map=$(pwd
 export LDFLAGS="-Wl,--build-id=none"
 export CXXFLAGS="${CFLAGS}"
 
-# Perl's Configure bakes the wall-clock build time into Config (cf_time/cf_by),
-# which makes the build non-reproducible. Pin both deterministically.
-export SOURCE_DATE_EPOCH="${SOURCE_DATE_EPOCH:-0}"
-CF_TIME="$(LC_ALL=C TZ=UTC date -u -d "@$SOURCE_DATE_EPOCH" 2>/dev/null || echo 'Thu Jan  1 00:00:00 UTC 1970')"
+# Perl's Configure recomputes cf_time from `date` UNCONDITIONALLY, so a
+# `-D cf_time=` override does NOT stick — the wall-clock still leaks into cf_time,
+# which feeds $config_tag1 (perlbug/perlthanks) and the "Configuration time" line
+# in Config_heavy.pl. config.over is sourced AFTER all of Configure's computation
+# (perl's documented override hook), so pin cf_time/cf_by there instead.
+# The sandbox already exports SOURCE_DATE_EPOCH — read it (with a fallback), don't re-set it.
+CF_TIME="$(LC_ALL=C TZ=UTC date -u -d "@${SOURCE_DATE_EPOCH:-0}" 2>/dev/null || echo 'Thu Jan  1 00:00:00 UTC 1970')"
+# Configure also bakes the build host's nodename (in the sandbox a per-build
+# `minimal-<pid>` hostname) into several Config fields: myuname (the "Target
+# system" line, via `uname -a`), myhostname, and the derived cf_email/perladmin.
+# config.over is sourced after all computation, so pin every host-derived field
+# here. myuname keeps the real kernel info with just the nodename sanitized.
+MYUNAME="$(uname -a | awk '{$2="builder"; print}' | tr '[:upper:]' '[:lower:]' | tr -d '/')"
+cat > config.over <<EOF
+cf_time='$CF_TIME'
+cf_by='builder'
+myuname='$MYUNAME'
+myhostname='builder'
+cf_email='build@builder'
+perladmin='build@builder'
+EOF
 
 sh Configure  -des                                          \
              -D cc=gcc                                     \
@@ -34,9 +51,7 @@ sh Configure  -des                                          \
              -D man3dir=/usr/share/man/man3                \
              -D pager="/usr/bin/less -isR"                 \
              -D useshrplib                                 \
-             -D usethreads                                  \
-             -D cf_time="$CF_TIME"                          \
-             -D cf_by=builder
+             -D usethreads
 
 make -j$(nproc)
 # TEST_JOBS=$(nproc) make test_harness # TODO there are failures