[balsa/52-fix-clang-9-fails] meson.build: Add -Wenum-conversion flag

[Peter Bloomfield <peterb src gnome org>]

commit e086fdbea97ac4282588f64ac6e35a80aa05ca29
Author: Peter Bloomfield <PeterBloomfield bellsouth net>
Date:   Mon Jan 11 17:54:39 2021 -0500

    meson.build: Add -Wenum-conversion flag
    
    It should be enabled by default, but doesn't seem to be. Meson's default
    warn-level uses -Wall, and the gcc docs say that that implies
    -Wenum-conversion. However, without the flag set explicitly, gcc does
    not detect enum-conversion errors. So we'll just set it.

 meson.build | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/meson.build b/meson.build
index d930e271b..8539d041b 100644
--- a/meson.build
+++ b/meson.build
@@ -456,6 +456,7 @@ if balsa_from_git
     '-Wformat',
     '-Wformat-security',
     '-Wignored-qualifiers',
+    '-Wenum-conversion',
     '-DGDK_DISABLE_DEPRECATED',
     '-DGMIME_DISABLE_DEPRECATED',
     '-DGTK_DISABLE_DEPRECATED',