Parse meson build has_header error output and automatically add build dependency

[gtkramer]

When building gnome-builder, after getting through 10 rounds, the build errors out with the following message:

Configuring ide-debug.h using configuration
src/libide/terminal/meson.build:7:3: ERROR: C header 'pcre2.h' not found

Autospec was not able to handle the output from the following check during the meson build:

# Ensure we have PCRE2 available
cc.has_header('pcre2.h', required: true)

[phmccarty]

Looks like the meson build requirement scan should be made more robust.