validate: Use gz compression during bindist check

Test Plan: validate, check that gz is used

Reviewers: hvr, austin, thomie

Reviewed By: thomie

Differential Revision: https://phabricator.haskell.org/D1788

GHC Trac Issues: #11434

mk/config.mk.in

@@ -768,7 +768,7 @@ GZIP_CMD       = gzip
 XZ_CMD         = xz -9e
 
 # xz is default compression
-TAR_COMP      = xz
+TAR_COMP      ?= xz
 
 # select compression command and .tar extension based on TAR_COMP value
 ifeq "$(TAR_COMP)" "bzip2"

validate

@@ -47,6 +47,10 @@ hpc=NO
 speed=NORMAL
 use_dph=0
 be_quiet=0
+# Validate uses gzip compression for the binary distribution to avoid the rather
+# heavy cost of xz, which is the typical default. The options are defined in
+# mk/config.mk.in
+tar_comp=gzip
 
 while [ $# -gt 0 ]
 do
@@ -211,8 +215,8 @@ check_packages post-build
 
 if [ $speed != "FAST" ]; then
 
-    $make binary-dist-prep
-    $make test_bindist TEST_PREP=YES
+    $make binary-dist-prep TAR_COMP=$tar_comp
+    $make test_bindist TEST_PREP=YES TAR_COMP=$tar_comp
 
     #
     # Install the xhtml package into the bindist.