The -Wl,xxx option for gcc passes a comma-separated list of tokens as a space-separated list of arguments to the linker. So
gcc -Wl,aaa,bbb,ccc
eventually becomes a linker call
ld aaa bbb ccc
In your case, you want to say “ld -rpath .“, so you pass this to gcc as -Wl,-rpath,. Alternatively, you can specify repeat instances of -Wl:
gcc -Wl,aaa -Wl,bbb -Wl,ccc
Note that there is no comma between aaa and the second -Wl.
Or, in your case, -Wl,-rpath -Wl,..