libssh: removed obsolete cmake related hack from .conf file

network/libssh/libssh.conf

@@ -15,9 +15,4 @@
 # apply the patches defined in the libssh.desc
 var_append patchfiles ' ' "`match_source_file -p patch`"
 
-pkg_libssh_premake() {
-	mkdir -p build
-	cd build
-	cmake -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=Release ..
-}
-hook_add premake 5 "pkg_libssh_premake"
+var_append cmakeopt ' ' "-DCMAKE_BUILD_TYPE=Release"