fix: removes soname loading eggs works, units fail

;; units as in built-ins (tcp, extras, files etc). eggs are installed
;; with android-chicken-install.
;;
;; On the target device: (prepl is an egg I installed)

@> (use prepl)
; loading /data/data/org.libsdl.app/lib//libprepl.import.so ...
; loading /data/data/org.libsdl.app/lib//libchicken.import.so ...
; loading /data/data/org.libsdl.app/lib//libsrfi-1.import.so ...
; loading /data/data/org.libsdl.app/lib//libports.import.so ...
; loading /data/data/org.libsdl.app/lib//libtcp.import.so ...
@> (use posix)
; loading /data/data/org.libsdl.app/lib//libposix.import.so ...
; loading library posix ...

Error: (load-library) unable to load library
posix
"dlopen failed: library \"libchicken.so.7\" not found"

	Call history:

	<syntax>	  (##core#quote posix)
	<syntax>	  (import posix)
	jni/src/main.scm:12: %##sys#find-extension
	jni/src/main.scm:13: string-append
	jni/src/main.scm:13: %##sys#find-extension
	<syntax>	  (##core#undefined)
	<syntax>	  (##core#undefined)
	<eval>	  (##sys#load-library (quote posix) #f)
	prepl.scm:43: k77
	prepl.scm:43: g81
	prepl.scm:44: print-error-message
	prepl.scm:45: print-call-chain	  	<--
fix: eval.scm: use soname only with when USES_SONAME present in Makefile

Android, who'se software-version is 'linux, does not use sonames and
crashes with (use <unit>) because the binary-version is incorrectly
appended to the shared library filename.

This patch explicitly propagates the Makefiles' USES_SONAME property
through to eval for this to work properly.