zstd: enable pzstd

hi,

here's a change to enable pzstd in archivers/zstd. pzstd can do parallel
de/compression, like pigz.

i built this locally and it seemed to produce the right binary, but i'm not
very familiar with ports yet, so apologies if this change is incomplete.

diff --git a/archivers/zstd/Makefile b/archivers/zstd/Makefile
index 3b6d18883ae..22dca58e7dd 100644
--- a/archivers/zstd/Makefile
+++ b/archivers/zstd/Makefile
@@ -44,6 +44,14 @@ TEST_TARGET = check
TESTTMP = ${WRKDIR}/tmp
TEST_ENV = TMPDIR=${TESTTMP}

+do-build:
+ ${SETENV} ${MAKE_ENV} ${MAKE_PROGRAM} ${MAKE_FLAGS} -C ${WRKSRC}
+ ${SETENV} ${MAKE_ENV} ${MAKE_PROGRAM} ${MAKE_FLAGS} -C ${WRKSRC}/contrib/pzstd
+
+do-install:
+ ${SETENV} ${MAKE_ENV} ${MAKE_PROGRAM} ${MAKE_FLAGS} -C ${WRKSRC} install
+ ${SETENV} ${MAKE_ENV} ${MAKE_PROGRAM} ${MAKE_FLAGS} -C ${WRKSRC}/contrib/pzstd install
+
pre-build:
ln -fs ${LOCALBASE}/bin/ggrep ${WRKDIR}/bin/grep

diff --git a/archivers/zstd/pkg/PLIST b/archivers/zstd/pkg/PLIST
index bd2756a9672..0215c741273 100644
--- a/archivers/zstd/pkg/PLIST
+++ b/archivers/zstd/pkg/PLIST
@@ -1,3 +1,4 @@
+@bin bin/pzstd
bin/unzstd
@bin bin/zstd
bin/zstdcat