ch32v: Fix: Add clobbers to bss/data loops

[Grazfather]

I noticed that ch32v examples were broken. git bisect got me to #868, but some debugging with @kibels suggested something else was going on.

Looks like those changes just exposed a bug where we weren't clobbering properly, so a subsequent CSR, which was using a register, had had it clobbered.

I haven't exactly tracked why this exposed the issue, since the csrwi instructions (only changed ones) are before the problematic function.

[github-actions]

🔍 Lint Results

[github-actions]

🔍 Lint Results

[Grazfather]

Making this change causes the issue to be exhibited (for me on zig 0.15.2). The clobbers fix the issue.

diff --git i/port/wch/ch32v/src/cpus/main.zig w/port/wch/ch32v/src/cpus/main.zig
index a477503d..c1192fd2 100644
--- i/port/wch/ch32v/src/cpus/main.zig
+++ w/port/wch/ch32v/src/cpus/main.zig
@@ -236,7 +236,7 @@ pub const startup_logic = struct {
         );

         // NOTE: this can only be called once. Otherwise, we get a linker error for duplicate symbols
-        startup_logic.initialize_system_memories();
+        microzig.utilities.initialize_system_memories(.auto);

         // Configure the CPU.
         switch (cpu_name) {

Even though the issue is 'far away', for me this caused the jal _system_init to happen AFTER putting &microzig_main into a register for the subsequent write to mepc.