tce-load -i gtk3-dev libsoup-dev geocode-glib-dev intltool tzdata gobject-introspection-dev vala-dev gtk3-gir

cd libgweather-3.20.3

CC="gcc -flto -fuse-linker-plugin -mtune=generic -Os -pipe" CXX="g++ -flto -fuse-linker-plugin -mtune=generic -Os -pipe -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local --disable-static --localstatedir=/var

find . -name Makefile -type f -exec sed -i 's/-g -O2//g' {} \;

make
sudo make install

libgweather-3.20.1 configure summary:

        Prefix:                         /usr/local
        Source code location:           .
        Compiler:                       gcc -flto -fuse-linker-plugin -mtune=generic -Os -pipe
        Introspection support:          yes
        Build Vala bindings:            yes