build-aux: add missing definition of PERL variable

Currently $(PERL) is expanding to nothing, but the spacing-check.pl test
luckily still works via the shebang.

Reviewed-by: Peter Krempa <pkrempa@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

build-aux/Makefile.in

@@ -6,6 +6,7 @@ FLAKE8 = @flake8_path@
 BLACK = @black_path@
 RUNUTF8 = @runutf8@
 PYTHON = @PYTHON3@
+PERL = @PERL@
 GREP = @GREP@
 SED = @SED@
 AWK = @AWK@

build-aux/meson.build

@@ -42,6 +42,7 @@ if git and tests_enabled[0]
     'black_path': black_path,
     'runutf8': ' '.join(runutf8),
     'PYTHON3': python3_prog.full_path(),
+    'PERL': perl_prog.full_path(),
     'GREP': grep_prog.full_path(),
     'SED': sed_prog.full_path(),
     'AWK': awk_prog.full_path(),