Preserve CMake options when make is invoked

BSDmakefile

@@ -20,20 +20,22 @@ _GENERATOR!=which ninja 2>/dev/null >/dev/null && echo Ninja || echo "Unix Makef
 GENERATOR?=$(_GENERATOR)
 
 .if $(GENERATOR) == "Ninja"
-BUILDFILE=build/build.ninja
+BUILDFILE=build.ninja
 .else
-BUILDFILE=build/Makefile
+BUILDFILE=Makefile
 .endif
 
 PREFIX?=/usr/local
 
+.PHONY: build/fish
 build/fish: build/$(BUILDFILE)
 	$(CMAKE) --build build
 
-build:
+# Don't split the mkdir into its own rule because that would cause CMake to regenerate the build 
+# files after each build (because it adds the mdate of the build directory into the out-of-date
+# calculation tree). GNUmake supports order-only dependencies, BSDmake does not seem to.
+build/$(BUILDFILE):
 	mkdir -p build
-
-build/$(BUILDFILE): build
 	cd build; $(CMAKE) .. -G "$(GENERATOR)" -DCMAKE_INSTALL_PREFIX="$(PREFIX)" -DCMAKE_EXPORT_COMPILE_COMMANDS=1
 
 .PHONY: install

GNUmakefile

@@ -31,15 +31,18 @@ else
 
 all: .begin build/fish
 
-PHONY: .begin
+.PHONY: .begin
 .begin:
 	@which $(CMAKE) > /dev/null 2> /dev/null || \
 		 (echo 'Please install CMake and then re-run the `make` command!' 1>&2 && false)
 
+.PHONY: build/fish
 build/fish: build/$(BUILDFILE)
 	$(CMAKE) --build build
 
-build/$(BUILDFILE): build
+# Use build as an order-only dependency. This prevents the target from always being outdated
+# after a make run, and more importantly, doesn't clobber manually specified CMake options.
+build/$(BUILDFILE): | build
 	cd build; $(CMAKE) .. -DCMAKE_EXPORT_COMPILE_COMMANDS=1 -G "$(GENERATOR)" \
 		-DCMAKE_INSTALL_PREFIX="$(PREFIX)" -DCMAKE_EXPORT_COMPILE_COMMANDS=1 \
 		-DCMAKE_BUILD_TYPE=RelWithDebInfo