Makefile: remove install target hack

This hack had some side effects. For instance when doing `make
android_x86 install` it would first do `make android_x86` and then `make
default install`. Correct would be to actually install the android_x86
lib.

This will break the doc generation which needs to be fixed using a
script in a later commit.

This change means that we can't just do `make install` but now need to
do `make default install`.

Makefile

@@ -70,10 +70,6 @@ all: default
 default:
 	$(call cmake-build)
 
-# install basically just runs default install
-install: ARGS += install
-install: default
-
 docs: install
 	- mkdir install/docs
 	- (cd install && doxygen ../.doxygen)