fix(mega65): fix crt0 + libprintf linkage

Author: kassane

build.zig

@@ -1680,6 +1680,11 @@ fn addMega65Exe(
     exe.root_module.linkLibrary(libs.crt);
     exe.root_module.linkLibrary(libs.crt0);
     exe.root_module.linkLibrary(libs.c);
+    if (libs.printf) |libprintf| exe.root_module.linkLibrary(libprintf);
+    if (libs.crt0_obj) |obj| exe.root_module.addObject(obj);
+    if (libs.mem) |mem_obj| exe.root_module.addObject(mem_obj);
+    exe.forceUndefinedSymbol("__zig_call_main_section");
+    exe.forceUndefinedSymbol("main");
     exe.setLibCFile(libc_txt);
     exe.root_module.link_libc = true;
     exe.setLinkerScript(wrapper_ld);

mega65/plasma/plasma.zig

@@ -129,34 +129,3 @@ export fn main() void {
     while (true) draw();
 }
 
-/// Satisfy crt0's __zero_bss / compiler-generated memory ops (no C stdlib linked).
-export fn __memset(dest: [*]u8, c: u32, n: usize) [*]u8 {
-    var i: usize = 0;
-    while (i < n) : (i += 1) dest[i] = @truncate(c);
-    return dest;
-}
-
-export fn memset(dest: [*]u8, c: c_int, n: usize) [*]u8 {
-    var i: usize = 0;
-    while (i < n) : (i += 1) dest[i] = @truncate(@as(c_uint, @bitCast(c)));
-    return dest;
-}
-
-export fn memcpy(noalias dest: [*]u8, noalias src: [*]const u8, n: usize) [*]u8 {
-    @memcpy(dest[0..n], src[0..n]);
-    return dest;
-}
-
-export fn memmove(dest: [*]u8, src: [*]const u8, n: usize) [*]u8 {
-    if (@intFromPtr(dest) < @intFromPtr(src)) {
-        var i: usize = 0;
-        while (i < n) : (i += 1) dest[i] = src[i];
-    } else {
-        var i: usize = n;
-        while (i > 0) {
-            i -= 1;
-            dest[i] = src[i];
-        }
-    }
-    return dest;
-}