diff --git a/Dockerfile b/Dockerfile
index bf1d1ee..1879b98 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,5 +1,5 @@
 FROM emscripten/emsdk:2.0.26
-RUN apt-get update && apt-get install -qqy autoconf autopoint libtool-bin pkg-config
+RUN apt-get update && apt-get install -qqy autoconf autopoint pkg-config
 WORKDIR /src
 ENV EM_CACHE /src/deps/.emcache
 CMD ["sh", "-c", "emmake make -j`nproc`"]
diff --git a/Makefile b/Makefile
index 2dd379e..cd62fb7 100644
--- a/Makefile
+++ b/Makefile
@@ -1,16 +1,25 @@
 SYSROOT = $(PWD)/deps/.install
-export PKG_CONFIG_PATH = $(SYSROOT)/lib/pkgconfig
 
+# Add custom sysroot to paths.
 export CPPFLAGS += -I$(SYSROOT)/include
-export LDFLAGS += -L$(SYSROOT)/lib -s DYNAMIC_EXECUTION=0 -s AUTO_JS_LIBRARIES=0 -s AUTO_NATIVE_LIBRARIES=0 -s ALLOW_UNIMPLEMENTED_SYSCALLS=0
+export LDFLAGS += -L$(SYSROOT)/lib
+export PATH := $(SYSROOT)/bin:$(PATH)
+export PKG_CONFIG_PATH = $(SYSROOT)/lib/pkgconfig
+export ACLOCAL_PATH := $(SYSROOT)/share/aclocal:$(ACLOCAL_PATH)
 
+# Common linking flags for all targets.
+export LDFLAGS += -s DYNAMIC_EXECUTION=0 -s AUTO_JS_LIBRARIES=0 -s AUTO_NATIVE_LIBRARIES=0 -s ALLOW_UNIMPLEMENTED_SYSCALLS=0
+
+# Common compilation & linking flags for all langs and targets.
 COMMON_FLAGS = -Os -flto
 export CFLAGS += $(COMMON_FLAGS)
 export CXXFLAGS += $(COMMON_FLAGS)
 export LDFLAGS += $(COMMON_FLAGS)
 
+## Main API module
+
 libapi.mjs: api.o $(SYSROOT)/lib/libltdl.la $(SYSROOT)/lib/libgphoto2.la
-	deps/libgphoto2/libtool --verbose --mode=link $(LD) $(LDFLAGS) -o $@ $+ \
+	libtool --verbose --mode=link $(LD) $(LDFLAGS) -o $@ $+ \
 		--bind -s ASYNCIFY -s ALLOW_MEMORY_GROWTH \
 		-dlpreopen $(SYSROOT)/lib/libgphoto2/2.5.27.1/ptp2.la \
 		-dlpreopen $(SYSROOT)/lib/libgphoto2_port/0.12.0/usb1.la
@@ -19,32 +28,46 @@ api.o: deps/libgphoto2/configure.ac
 api.o: CPPFLAGS += -Ideps/libgphoto2 -Ideps/libgphoto2/libgphoto2_port
 api.o: CXXFLAGS += -std=c++17 -fexceptions
 
-$(SYSROOT)/.exists:
+## Generic rules for deps
+
+$(SYSROOT):
 	mkdir -p $(@D)
-	touch $@
+
+## libtool
 
 deps/libtool/configure:
 	mkdir -p deps/libtool
 	curl -L https://ftpmirror.gnu.org/libtool/libtool-2.4.6.tar.gz | tar zx --strip 1 -C deps/libtool
 
+deps/libtool/Makefile: deps/libtool/configure
+	cd $(@D) && ./configure --prefix=$(SYSROOT) --disable-shared
+
+$(SYSROOT)/lib/libltdl.la: deps/libtool/Makefile | $(SYSROOT)
+	$(MAKE) -C deps/libtool install
+
+## libgphoto2
+
 deps/libgphoto2/configure.ac deps/libusb/configure.ac &:
 	git submodule update --init
 
-$(SYSROOT)/lib/libltdl.la: $(SYSROOT)/.exists deps/libtool/configure
-	cd deps/libtool && \
-	./configure --prefix=$(SYSROOT) --disable-shared && \
-	$(MAKE) install
+deps/libgphoto2/configure: deps/libusb/configure.ac | $(SYSROOT)/lib/libltdl.la
+	cd $(@D) && autoreconf -fiv
 
-$(SYSROOT)/lib/libusb-1.0.la: $(SYSROOT)/.exists deps/libusb/configure.ac
-	cd deps/libusb && \
-	autoreconf -fiv && \
-	./configure --prefix=$(SYSROOT) --disable-shared --host=wasm32 && \
-	$(MAKE) install
-
-$(SYSROOT)/lib/libgphoto2.la: deps/libgphoto2/configure.ac $(SYSROOT)/lib/libltdl.la $(SYSROOT)/lib/libusb-1.0.la
-	cd deps/libgphoto2 && \
-	autoreconf -fiv && \
+deps/libgphoto2/Makefile: deps/libgphoto2/configure | $(SYSROOT)/lib/libusb-1.0.la
 	./configure --prefix=$(SYSROOT) --disable-shared --host=wasm32 \
 		 --without-libxml-2.0 --disable-nls --disable-ptpip --disable-disk \
-		 --with-camlibs=ptp2 && \
-	$(MAKE) install
+		 --with-camlibs=ptp2
+
+$(SYSROOT)/lib/libgphoto2.la: deps/libgphoto2/Makefile $(SYSROOT)/lib/libusb-1.0.la $(SYSROOT)/lib/libltdl.la
+	$(MAKE) -C deps/libgphoto2 install
+
+## libusb
+
+deps/libusb/configure: deps/libusb/configure.ac | $(SYSROOT)/lib/libltdl.la
+	cd $(@D) && autoreconf -fiv
+
+deps/libusb/Makefile: deps/libusb/configure
+	cd $(@D) && ./configure --prefix=$(SYSROOT) --disable-shared --host=wasm32
+
+$(SYSROOT)/lib/libusb-1.0.la: deps/libusb/Makefile
+	$(MAKE) -C deps/libusb install
diff --git a/build.sh b/build.sh
index a3b05f1..277773a 100755
--- a/build.sh
+++ b/build.sh
@@ -3,4 +3,5 @@ docker build -t web-gphoto2 - < Dockerfile
 docker run --rm -it \
 	-v $PWD:/src \
 	-u $(id -u):$(id -g) \
-	web-gphoto2
+	web-gphoto2 \
+	$@