Fixed typo (missing comma between 'musl' and 'uclibc')

Author: TommyMurphyTM1234

.github/workflows/build.yaml

@@ -14,7 +14,7 @@ jobs:
     strategy:
       matrix:
         os:     [ubuntu-22.04, ubuntu-24.04]
-        mode:   [newlib, linux, musl uclibc]
+        mode:   [newlib, linux, musl, uclibc]
         target: [rv32gc-ilp32d, rv64gc-lp64d]
         compiler: [gcc, llvm]
         exclude: