For some reason find command didn't understand the command line. If
anything is prepended to the command line, it starts to work.
$(Q)$(CC) --shared -Xlinker -soname=lib$(1).$(SOLIB_EXT) -o $$@ $$($(1)_objslo) $$(LOADLIBES) $$($(1)_libs:%=-l%)
endef
--include $(shell find $(USER_BUILD_DIR) -name 'lib*.omkvar')
+-include $(shell true; find $(USER_BUILD_DIR) -name 'lib*.omkvar') # `true' is a hack for MinGW
#$(warning $(shared_libs))
$(foreach lib,$(shared_libs),$(eval $(call solib_link_template,$(lib))))