Extend semantic for option '--with-extra-multilib-test'

The `--with-extra-multilib-test` take the format like below for now.

"<arch>-<abi>-[code-model][;<arch>-<abi>-[code-model]*"

This patch would like to extend the sematic to support additional buil
options for each combination. Aka:

"<arch>-<abi>-[code-model][:opts]*[;<arch>-<abi>-[code-model][:opts]*]*"

opts can be one or more build options splited by ':'. For example as
below:

* --param=riscv-autovec-lmul=m1
* --param=riscv-autovec-lmul=dynamic:--param=riscv-autovec-preference=fixed-vlmax

Thus the full example of the option `--with-extra-multilib-test` will be:

`rv64gcv_zvl128b-lp64d:--param=riscv-autovec-lmul=m1;rv64gcv_zvl256b-lp64d:-
-param=riscv-autovec-lmul=dynamic:--param=riscv-autovec-preference=fixed-vlmax`

Signed-off-by: Pan Li <pan2.li@intel.com>