meson: Add some missing env settings for tests of pg_dump and pg_verifybackup

The commands used for the compression tests were missing in a few
places, causing the tests related to these to never run.

Georgios has spotted GZIP_PROGRAM missing in pg_dump, while I have
noticed the ones missing in pg_verifybackup while looking at the rest of
the tree.

Author: Georgios Kokolatos, Michael Paquier
Discussion: https://postgr.es/m/O4mutIrCES8ZhlXJiMvzsivT7ztAMja2lkdL1LJx6O5f22I2W8PBIeLKz7mDLwxHoibcnRAYJXm1pH4tyUNC4a8eDzLn22a6Pb1S74Niexg=@pm.me

src/bin/pg_dump/meson.build

@@ -82,6 +82,7 @@ tests += {
   'sd': meson.current_source_dir(),
   'bd': meson.current_build_dir(),
   'tap': {
+    'env': {'GZIP_PROGRAM': gzip.path()},
     'tests': [
       't/001_basic.pl',
       't/002_pg_dump.pl',

src/bin/pg_verifybackup/meson.build

@@ -21,6 +21,10 @@ tests += {
   'sd': meson.current_source_dir(),
   'bd': meson.current_build_dir(),
   'tap': {
+    'env': {'GZIP_PROGRAM': gzip.path(),
+            'TAR': tar.path(),
+            'LZ4': program_lz4.found() ? program_lz4.path() : '',
+            'ZSTD': program_zstd.found() ? program_zstd.path() : ''},
     'tests': [
       't/001_basic.pl',
       't/002_algorithm.pl',