Revert "Merge pull request #11804 from obsidiansystems/remove-old-make"

This reverts commit 619eeb658a, reversing
changes made to 1af94bf471.

mk/functions.mk

@@ -0,0 +1,14 @@
+# Utility function for recursively finding files, e.g.
+# ‘$(call rwildcard, path/to/dir, *.c *.h)’.
+rwildcard=$(foreach d,$(wildcard $1*),$(call rwildcard,$d/,$2) $(filter $(subst *,%,$2),$d))
+
+# Given a file name, produce the corresponding dependency file
+# (e.g. ‘foo/bar.o’ becomes ‘foo/.bar.o.dep’).
+filename-to-dep = $(dir $1).$(notdir $1).dep
+
+# Return the full path to a program by looking it up in $PATH, or the
+# empty string if not found.
+find-program = $(shell for i in $$(IFS=: ; echo $$PATH); do p=$$i/$(strip $1); if [ -e $$p ]; then echo $$p; break; fi; done)
+
+# Ensure that the given string ends in a single slash.
+add-trailing-slash = $(patsubst %/,%,$(1))/