Bump gcc

Backport following patches from upstream:

 - RISC-V: Check multiletter extension has more than 1 letter
 - RISC-V: Add configure option: --with-multilib-generator to flexible config multi-lib settings.
 - RISC-V: Refine riscv_parse_arch_string
 - RISC-V: Extend syntax for the multilib-generator
 - RISC-V: Handle implied extension in multilib-generator
 - RISC-V: Add support for -mcpu option.
 - RISC-V: Define __riscv_cmodel_medany for PIC mode.

riscv-gcc

@@ -1 +1 @@
-Subproject commit ccddbbc098c2f736bd05c42f9762eebae9f0ef6f
+Subproject commit 07ec304392f0e16e6e80e777ce6a0afe8ae35a0b