icu: set missing RPATH. disable static library explicitly.

@kazuhiko also says:

with our current usage on gitlab, missing RPATH is not an issue but if
you invoke './parts/icu/bin/makeconv', it fails before my change.

/reviewed-by @kirr
/reviewed-on nexedi/slapos!62

component/icu/buildout.cfg

@@ -8,7 +8,10 @@ location = ${buildout:parts-directory}/${:_buildout_section_name_}
 url = http://download.icu-project.org/files/icu4c/4.8.1.1/icu4c-4_8_1_1-src.tgz
 md5sum = ea93970a0275be6b42f56953cd332c17
 configure-command = source/configure
-configure-options = --prefix=${:location}
+configure-options =
+  --prefix=${:location}
+  --disable-static
+  --enable-rpath
 
 [icu]
 <= icu4c