Add CI for --disable-asm.

CI currently does not thoroughly test encoding and decoding (except for
encoding zeroed dummy frames).
Testing --disable-asm is still useful because it ensures that the code compiles
on platforms where there are no ASM optimizations and the generic C code paths
are used.

.gitlab-ci.yml

@@ -53,6 +53,11 @@ autotools-clang:
     CONFIG_FLAGS: CFLAGS=-Wreserved-identifier
     CC: clang
 
+autotools-disable-asm:
+  extends: .autoconf
+  variables:
+    CONFIG_FLAGS: --disable-asm
+
 autotools-disable-encoding:
   extends: .autoconf
   variables: