ext-toolchain.sh: rework generated gcc wrapper Only append -L and...

ext-toolchain.sh: rework generated gcc wrapper Only append -L and -Wl,-rpath-link flags if the command line contains -l, -L, -shared or -static flags; this is needed to suppress "-rpath-link: linker input file unused because linking not done" on each cc invocation.

SVN-Revision: 29946