tce-load -i compiletc meson gtk4-dev gtk4-gir pcre21042-dev.tcz gobject-introspection-dev vala-dev

wget https://download.gnome.org/sources/gtksourceview/5.12/gtksourceview-5.12.0.tar.xz

cd gtksourceview-5.12.0

mkdir build
cd build

CC="gcc -mtune=generic -Os -pipe" CXX="g++ -mtune=generic -Os -pipe -fno-exceptions -fno-rtti" meson --prefix=/usr/local --localstatedir=/var --buildtype=plain

[flto fails]

ninja [0m 51.80s]
sudo ninja install

gtksourceview 5.12.0

    Documentation  : NO
    Build Testsuite: YES
    Install tests  : NO
    Introspection  : YES
    Vala vapi      : YES

  User defined options
    buildtype      : plain
    localstatedir  : /var
    prefix         : /usr/local