libssh2: disable rpath to fix curl-native build

When curl is built with PACKAGECONFIG:append = " libssh2", the build fails
with the error:
gcc: error: unrecognized command-line option '-R'

It was trying to set the rpath for libssh2.

(From OE-Core rev: c213d8579951e168a19231cf5b2f81d55e059a22)

Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-support/libssh2/libssh2_1.11.0.bb

@@ -18,6 +18,7 @@ inherit autotools pkgconfig ptest
 EXTRA_OECONF += "\
                  --with-libz \
                  --with-libz-prefix=${STAGING_LIBDIR} \
+                 --disable-rpath \
                 "
 DISABLE_STATIC = ""