If you want to override /usr/local as the default prefix
(which means /usr/local/include would have the header file and
/usr/local/lib would have the library files), then run
make, make install and make uninstall (to build, to
install and uninstall respectively - you need it for
all three as I explain below) :

make PREFIX=/tmp
make PREFIX=/tmp install
make PREFIX=/tmp uninstall

The last two will of course have to be done
as root if you need permissions to write to
the directory (for /tmp you wouldn't unless
the files already existed by someone else and
you didn't have permission).

In any case, the above would install header file
under '/tmp/include' and the library file(s) under
'/tmp/lib'.

If you want to know the technical details as to why
you have to (when overriding the install location)
specify PREFIX= even when building, see the FAQ
file (summary: it makes it easier for you when linking
in the shared library).

A word of caution to those overriding prefix :
--
You are more than welcome to disregard this but I feel
it is something I should bring up. If you do override
the prefix I strongly recommend you do not specify
'/usr'. Why one might ask. The typical way is
that user-compiled programs/libraries/etc. go under
'/usr/local' (other times '/opt'). This has multiple
benefits: you keep '/usr' clean and if you have a
package manager then it makes it easy to say:
"The only files under /usr/include and /usr/lib are
those that belong to a package."
In other words it is easier to maintain integrity
and verify everything. Most important of it all
(aside the security implications) is this:
You have less chance of name clashes. If there ever
is a package that installs to /usr and it includes
the files (maybe a package for AngelScript) then you
will have issues.
--

Lastly: I don't have a way to test the phone builds
so I cannot verify the build process (it really
depends on the environment and architecture, like
most things); I'm an old-timer that hates the
"smart" trend (besides: it is a horrible misuse
of the world 'smart').

CONTACT:
If you have any questions or concerns, by all
means have Andreas contact me (at this time I
don't have an email I feel okay sharing - if it
seems this is of use to others I will likely
create an email on my server for this very
purpose). For now Andreas can forward the
message to me.