Set non-/games paths, respect FLAGS, add LIBS to pass them in right order,
use pkg-config, don't strip, and show commands/errors directly.

https://bugs.gentoo.org/125550
https://bugs.gentoo.org/126835
https://bugs.gentoo.org/234013
--- a/Makefile
+++ b/Makefile
@@ -15,4 +15,4 @@
 PREFIX=/usr/local
-DATADIR=$(PREFIX)/share/games/flobopuyo
-INSTALL_BINDIR=$(DESTDIR)/$(PREFIX)/games
+DATADIR=$(PREFIX)/share/flobopuyo
+INSTALL_BINDIR=$(DESTDIR)/$(PREFIX)/bin
 INSTALL_DATADIR=$(DESTDIR)/$(DATADIR)
@@ -44,10 +44,10 @@
 CC=g++
-CXX=g++
 
-CFLAGS= -DDATADIR=\"${DATADIR}\"
-LDFLAGS=
+CFLAGS:=$(CXXFLAGS) $(CPPFLAGS) -DDATADIR=\"$(DATADIR)\"
 
 ifneq ($(PLATFORM), $(CYGWIN_VERSION))
-CFLAGS:=$(CFLAGS) `$(SDL_CONFIG) --cflags` -I/sw/include
-LDFLAGS:=$(LDFLAGS) `$(SDL_CONFIG) --cflags --libs`
+OPENGL-false=
+OPENGL-$(ENABLE_OPENGL)=opengl
+CFLAGS:=$(CFLAGS) $(shell $(PKG_CONFIG) --cflags $(OPENGL-true) sdl SDL_image SDL_mixer)
+LIBS:=$(LIBS) $(shell $(PKG_CONFIG) --libs $(OPENGL-true) sdl SDL_image SDL_mixer)
 endif
@@ -92,3 +92,2 @@
 ifeq ($(PLATFORM), Linux)
-LDFLAGS:=$(LDFLAGS) -lGL
 endif
@@ -112,3 +111,3 @@
 flobopuyo: ${OBJFILES}
-	@echo "[flobopuyo]" && g++ $(CFLAGS) $(LDFLAGS) -o flobopuyo -lSDL_mixer -lSDL_image ${OBJFILES}
+	$(CXX) $(CXXFLAGS) $(LDFLAGS) -o flobopuyo $(OBJFILES) $(LIBS)
 	@echo "--------------------------------------"
@@ -127,6 +126,6 @@
 %.o:%.c
-	@echo "[$@]" && $(CC) $(CFLAGS) -c $< 2>> WARNINGS || (cat WARNINGS && false)
+	$(CXX) $(CXXFLAGS) -c $<
 
 %.o:%.cpp
-	@echo "[$@]" && $(CXX) $(CFLAGS) -c $< 2>> WARNINGS || (cat WARNINGS && false)
+	$(CXX) $(CXXFLAGS) -c $<
 
@@ -157,6 +156,6 @@
 glSDL.o:glSDL.c
-	@echo "[$@]" && $(CC) $(CFLAGS) -c $< 2>> EXT_WARNINGS
+	$(CXX) $(CXXFLAGS) -c $<
 	@rm -f EXT_WARNINGS
 SDL_prim.o:SDL_prim.c
-	@echo "[$@]" && $(CC) $(CFLAGS) -c $< 2>> EXT_WARNINGS
+	$(CXX) $(CXXFLAGS) -c $<
 	@rm -f EXT_WARNINGS
@@ -180,3 +179,2 @@
 install: flobopuyo
-	strip flobopuyo
 	mkdir -p ${INSTALL_BINDIR}