The `perl` variable in meson.build is assigned to a program lookup,
which may have the value "not-found object" if configuring with
`-Dperl=disabled`.

There is already a list of other cases where we do need a perl command,
even when not building perl bindings. Building documentation should be
one of those cases, but was missing from the list. Add it.

Fixes:

$ meson setup builddir/ -Ddocs=man -Dperl=disabled -Dtests=false
[...]
Documentation/meson.build:308:22: ERROR: Tried to use not-found external program in "command"

Bug: https://bugs.gentoo.org/949247
Signed-off-by: Eli Schwartz <redacted>
---
 meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/meson.build b/meson.build
index efe2871c9d..c6241c7a12 100644
--- a/meson.build
+++ b/meson.build

@@ -772,7 +772,7 @@ endif
 # features. It is optional if you want to neither execute tests nor use any of
 # these optional features.
 perl_required = get_option('perl')
-if get_option('tests') or get_option('gitweb').enabled() or 'netrc' in get_option('credential_helpers')
+if get_option('tests') or get_option('gitweb').enabled() or 'netrc' in get_option('credential_helpers') or get_option('docs') != []
   perl_required = true
 endif
 

-- 
2.48.1