Avoid realpath, no available on macOS 12.x

Makefile

@@ -636,7 +636,7 @@ $(BIN)/BootROMs/%.bin: BootROMs/%.asm $(OBJ)/BootROMs/SameBoyLogo.pb12
 
 # Libretro Core (uses its own build system)
 libretro:
-	CFLAGS="$(WARNINGS)" $(MAKE) -C libretro BOOTROMS_DIR=$(BOOTROMS_DIR) BIN=$(BIN)
+	CFLAGS="$(WARNINGS)" $(MAKE) -C libretro BOOTROMS_DIR=$(abspath $(BOOTROMS_DIR)) BIN=$(abspath $(BIN))
 
 # install for Linux/FreeDesktop/etc.
 # Does not install mimetype icons because FreeDesktop is cursed abomination with no right to exist.

libretro/Makefile

@@ -328,11 +328,10 @@ endif
 
 ifeq ($(STATIC_LINKING), 1)
 # For some reason libretro's buildbot expects the output to be at ./libretro/ for static targets
-BIN ?= $(realpath -m $(CORE_DIR)/libretro)
+BIN ?= $(abspath $(CORE_DIR)/libretro)
 else
-BIN ?= $(realpath -m $(CORE_DIR))
+BIN ?= $(abspath $(CORE_DIR))
 endif
-override BIN := $(shell cd .. && realpath -m $(BIN))
 TARGET := $(BIN)/$(TARGET)
 
 
@@ -373,8 +372,6 @@ CFLAGS   += -D__LIBRETRO__ $(fpic) $(INCFLAGS) -std=gnu11 -D_GNU_SOURCE -D_USE_M
 
 all: $(TARGET)
 
-override BOOTROMS_DIR := $(shell cd .. && realpath -m $(BOOTROMS_DIR))
-
 $(CORE_DIR)/libretro/%_boot.c: $(BOOTROMS_DIR)/%_boot.bin
 	echo "/* AUTO-GENERATED */" > $@
 	echo "const unsigned char $(notdir $(@:%.c=%))[] = {" >> $@