webkitgtk provides a webkit2gtk-web-extension-4.0 .pc file for
webkitgtk web extensions, use it for the web extension.
Please note that ATM both `--cflags' and `--libs' webkit2gtk-4.0
and webkit2gtk-web-extension-4.0 returns the same values but if
they will diverge in the future the web extension will then use
the right `.pc'.
# flags used to build webextension
EXTTARGET = webext_main.so
-EXTCFLAGS = ${CFLAGS} $(shell pkg-config --cflags webkit2gtk-4.0)
+EXTCFLAGS = ${CFLAGS} $(shell pkg-config --cflags webkit2gtk-web-extension-4.0)
EXTCPPFLAGS = $(CPPFLAGS)
-EXTLDFLAGS = $(shell pkg-config --libs webkit2gtk-4.0) -shared
+EXTLDFLAGS = $(shell pkg-config --libs webkit2gtk-web-extension-4.0) -shared
# flags used for the main application
CFLAGS += $(shell pkg-config --cflags $(LIBS))