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[xparq]

#!!Would fail with fatal error U1037 dunno how to make *.ixx, if they don't happen to exist!
#!!objs:: $(src_dir)/$(units_pattern).ixx
#!!	@$(MAKE) -nologo RECURSED_FOR_COMPILING=1 DIR=$(DIR) $(patsubst $(src_dir)/%,$(obj_dir)/%,$(**:.ixx=.ifc))

To avoid the issue when a given source type -- used as a wildcard dependency
-- doesn't exist in the given source dir, this hackey won't work, because they
will catch all the existing cases, too:

$(src_dir)/$(units_pattern).cpp:
#!! Well, no `%|eF` either: it "requires a dependent"! ;)
	@echo Bu! Silencing the "Dunno how to make *.cpp" error, when no such file exists.
$(src_dir)/$(units_pattern).cxx:
	@echo Bu! Silencing the "Dunno how to make *.cxx" error, when no such file exists.
$(src_dir)/$(units_pattern).c:
	@echo Bu! Silencing the "Dunno how to make *.c" error, when no no such file exists.
$(src_dir)/$(units_pattern).ixx:
	@echo Bu! Silencing the "Dunno how to make *.ixx" error, when no no such file exists.

To mitigate the stupid "can't build unmatched wildcard" error, the combined
objs: c* rule can (coincidentally...) cover in one rule the cases, where
at least some .c* source exists in the given dir...