Include RV64 in SCU build

The single-compilation unit build `monolithic_build/mlkem_native_monobuild.c`
did previously not include the new RV64 backend. This commit adjusts
`scripts/autogen` to fix this.

Signed-off-by: Hanno Becker <beckphan@amazon.co.uk>

Author: hanno-becker

examples/monolithic_build/mlkem_native_monobuild.c

@@ -87,6 +87,9 @@
 #include "mlkem/native/x86_64/src/rej_uniform_avx2.c"
 #include "mlkem/native/x86_64/src/rej_uniform_table.c"
 #endif /* MLK_SYS_X86_64 */
+#if defined(MLK_SYS_RISCV64)
+#include "mlkem/native/riscv64/src/rv64v_poly.c"
+#endif
 #endif /* MLK_CONFIG_MONOBUILD_WITH_NATIVE_ARITH */
 
 #if defined(MLK_CONFIG_MONOBUILD_WITH_NATIVE_FIPS202)

scripts/autogen

@@ -1162,6 +1162,9 @@ def gen_monolithic_source_file(dry_run=False):
     def x86_64(c):
         return "x86_64" in c
 
+    def riscv64(c):
+        return "riscv64" in c
+
     def native_fips202(c):
         return native(c) and fips202(c)
 
@@ -1177,6 +1180,9 @@ def gen_monolithic_source_file(dry_run=False):
     def native_arith_aarch64(c):
         return native_arith(c) and aarch64(c)
 
+    def native_arith_riscv64(c):
+        return native_arith(c) and riscv64(c)
+
     def native_arith_x86_64(c):
         return native_arith(c) and x86_64(c)
 
@@ -1280,6 +1286,10 @@ def gen_monolithic_source_file(dry_run=False):
         for c in filter(native_arith_x86_64, c_sources):
             yield f'#include "{c}"'
         yield "#endif"
+        yield "#if defined(MLK_SYS_RISCV64)"
+        for c in filter(native_arith_riscv64, c_sources):
+            yield f'#include "{c}"'
+        yield "#endif"
         yield "#endif"
         yield ""
         yield "#if defined(MLK_CONFIG_MONOBUILD_WITH_NATIVE_FIPS202)"