[devhelp] build: pkg-config file: add the math library to libraries_private

[Sébastien Wilmet <swilmet src gnome org>]

commit ace85467e0d09fdc7711728c95f23d2bd62c9d8d
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Sat Apr 4 02:16:34 2020 +0200

    build: pkg-config file: add the math library to libraries_private
    
    It needs to be added as a string, unfortunately.

 devhelp/meson.build | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/devhelp/meson.build b/devhelp/meson.build
index 21165ac1..ce888f7c 100644
--- a/devhelp/meson.build
+++ b/devhelp/meson.build
@@ -122,6 +122,7 @@ PKG_CONFIG.generate(
   description: meson.project_name(),
   version: meson.project_version(),
   libraries: libdevhelp,
+  libraries_private: '-lm',
   subdirs: install_headers_first_subdir,
   requires: LIBDEVHELP_PUBLIC_DEPS,
   requires_private: LIBDEVHELP_PRIVATE_DEPS