diff --git a/Makefile b/Makefile
index 4137950..c0c0861 100644
--- a/Makefile
+++ b/Makefile
@@ -2,8 +2,9 @@
 # SporeModLoader & SporeModManager Makefile
 #
 
+THIRDPARTY_DIR := 3rdParty
 # relative to project directories
-BINARY_DIR := ../bin
+BINARY_DIR     := ../bin
 
 CC         := gcc
 CXX        := g++
@@ -19,13 +20,21 @@ clean:
 	$(MAKE) -C SporeModManager clean BINARY_DIR=$(BINARY_DIR)/SporeModLoader/SporeModManager
 	$(MAKE) -C SporeModManager clean MINGW=1 BINARY_DIR=$(BINARY_DIR)/SporeModLoader/SporeModManager
 
+# this is needed due to compiling SporeModLoader twice,
+# which, when compiling with multiple threads, will cause
+# zconf.h to be generated twice, causing a build failure
+# due to a race condition (cp will fail due to the file
+# already existing, even with -f)
+$(THIRDPARTY_DIR)/zlib/zconf.h: $(THIRDPARTY_DIR)/zlib/zconf.h.in
+	$(MAKE) -C SporeModManager ../$@
+
 SporeModLoader:
 	$(MAKE) -C $@ BINARY_DIR=$(BINARY_DIR)/SporebinEP1
 
-SporeModManager:
+SporeModManager: $(THIRDPARTY_DIR)/zlib/zconf.h
 	$(MAKE) -C $@ BINARY_DIR=$(BINARY_DIR)/SporeModLoader/SporeModManager
 
-SporeModManager.exe:
+SporeModManager.exe: $(THIRDPARTY_DIR)/zlib/zconf.h
 	$(MAKE) -C $(basename $@) BINARY_DIR=$(BINARY_DIR)/SporeModLoader/SporeModManager MINGW=1
 
 .PHONY: SporeModLoader SporeModManager SporeModManager.exe all clean
diff --git a/SporeModLoader/Makefile b/SporeModLoader/Makefile
index 999ec21..17f81ce 100644
--- a/SporeModLoader/Makefile
+++ b/SporeModLoader/Makefile
@@ -44,14 +44,12 @@ endif
 
 all: $(BINARY_DIR)/$(DLL_FILE)
 
-$(BINARY_DIR):
-	$(QUIET)mkdir -p $@
-
-$(BINARY_DIR)/$(DLL_FILE): $(BINARY_DIR) $(THIRDPARTY_OBJECT_FILES) $(OBJECT_FILES)
+$(BINARY_DIR)/$(DLL_FILE): $(THIRDPARTY_OBJECT_FILES) $(OBJECT_FILES)
 	@echo "MINGW_LD  $@"
+	$(QUIET)mkdir -p $(BINARY_DIR)
 	$(QUIET)$(MINGW_CXX) $(THIRDPARTY_OBJECT_FILES) $(OBJECT_FILES) -static -shared $(SOURCE_DIR)/dllmain.def -o $@ $(LDFLAGS)
 
 clean:
 	rm -f $(BINARY_DIR)/$(DLL_FILE) $(OBJECT_FILES) $(THIRDPARTY_OBJECT_FILES) $(THIRDPARTY_HEADER_FILES)
 
-.PHONY: all clean
\ No newline at end of file
+.PHONY: all clean
diff --git a/SporeModManager/Makefile b/SporeModManager/Makefile
index 519654e..9481eed 100644
--- a/SporeModManager/Makefile
+++ b/SporeModManager/Makefile
@@ -1,12 +1,12 @@
 #
 # SporeModManager Makefile
 #
-THIRDPARTY_DIR ?= ../3rdParty
-BINARY_DIR     ?= bin
-SOURCE_DIR     ?= .
-EXE_FILE       ?= SporeModManager
-VERBOSE        ?= 0
-MINGW          ?= 0
+THIRDPARTY_DIR := ../3rdParty
+BINARY_DIR     := bin
+SOURCE_DIR     := .
+EXE_FILE       := SporeModManager
+VERBOSE        := 0
+MINGW          := 0
 
 CC         ?= gcc
 CXX        ?= g++
@@ -22,7 +22,7 @@ else
 # mingw doesn't like LTO
 # and we need to statically link
 LDFLAGS    := -s -municode -static
-OPTFLAGS   := -Os
+OPTFLAGS   := -Os -flto
 OBJ        := obj
 EXE_EXT    := .exe
 endif
@@ -90,19 +90,18 @@ endif
 
 all: $(BINARY_DIR)/$(EXE_FILE)$(EXE_EXT)
 
-$(BINARY_DIR):
-	$(QUIET)mkdir -p $@
-
-$(THIRDPARTY_DIR)/zlib/zconf.h:
+$(THIRDPARTY_DIR)/zlib/zconf.h: $(THIRDPARTY_DIR)/zlib/zconf.h.in
 	@echo "GEN $@"
 	$(QUIET)cp -f $@.in $@
 
-$(BINARY_DIR)/$(EXE_FILE): $(BINARY_DIR) $(THIRDPARTY_OBJECT_FILES) $(OBJECT_FILES)
+$(BINARY_DIR)/$(EXE_FILE): $(THIRDPARTY_OBJECT_FILES) $(OBJECT_FILES)
 	@echo "LD  $@"
+	$(QUIET)mkdir -p $(BINARY_DIR)
 	$(QUIET)$(CXX) $(OBJECT_FILES) $(THIRDPARTY_OBJECT_FILES) -o $@ $(LDFLAGS)
 
-$(BINARY_DIR)/$(EXE_FILE).exe: $(BINARY_DIR) $(THIRDPARTY_OBJECT_FILES) $(OBJECT_FILES)
+$(BINARY_DIR)/$(EXE_FILE).exe: $(THIRDPARTY_OBJECT_FILES) $(OBJECT_FILES)
 	@echo "MINGW_LD  $@"
+	$(QUIET)mkdir -p $(BINARY_DIR)
 	$(QUIET)$(MINGW_CXX) $(OBJECT_FILES) $(THIRDPARTY_OBJECT_FILES) -o $@ $(LDFLAGS)
 
 clean: