Update zig build system to support user defined options

 * Fix assertion failure when switching on type.
   Closes #310
 * Update zig build system to support user defined options.
   See #204
 * fmt.format supports {sNNN} to set padding for a buffer arg.
 * add std.fmt.bufPrint and std.fmt.allocPrint
 * std.hash_map.HashMap.put returns the previous value
 * add std.mem.startsWith

src/ir.cpp

@@ -57,6 +57,7 @@ static TypeTableEntry *ir_analyze_instruction(IrAnalyze *ira, IrInstruction *ins
 static IrInstruction *ir_implicit_cast(IrAnalyze *ira, IrInstruction *value, TypeTableEntry *expected_type);
 
 ConstExprValue *const_ptr_pointee(ConstExprValue *const_val) {
+    assert(const_val->type->id == TypeTableEntryIdPointer);
     assert(const_val->special == ConstValSpecialStatic);
     switch (const_val->data.x_ptr.special) {
         case ConstPtrSpecialInvalid:
@@ -10350,10 +10351,21 @@ static TypeTableEntry *ir_analyze_instruction_switch_target(IrAnalyze *ira,
     if (type_is_invalid(target_value_ptr->value.type))
         return ira->codegen->builtin_types.entry_invalid;
 
+    if (target_value_ptr->value.type->id == TypeTableEntryIdMetaType) {
+        assert(instr_is_comptime(target_value_ptr));
+        TypeTableEntry *ptr_type = target_value_ptr->value.data.x_type;
+        assert(ptr_type->id == TypeTableEntryIdPointer);
+        ConstExprValue *out_val = ir_build_const_from(ira, &switch_target_instruction->base);
+        out_val->type = ira->codegen->builtin_types.entry_type;
+        out_val->data.x_type = ptr_type->data.pointer.child_type;
+        return out_val->type;
+    }
+
     assert(target_value_ptr->value.type->id == TypeTableEntryIdPointer);
+
     TypeTableEntry *target_type = target_value_ptr->value.type->data.pointer.child_type;
     ConstExprValue *pointee_val = nullptr;
-    if (target_value_ptr->value.special != ConstValSpecialRuntime) {
+    if (instr_is_comptime(target_value_ptr)) {
         pointee_val = const_ptr_pointee(&target_value_ptr->value);
         if (pointee_val->special == ConstValSpecialRuntime)
             pointee_val = nullptr;

src/main.cpp

@@ -167,9 +167,8 @@ int main(int argc, char **argv) {
         ZigList<const char *> args = {0};
         args.append(zig_exe_path);
         for (int i = 2; i < argc; i += 1) {
-            if (strcmp(argv[i], "--verbose") == 0) {
+            if (strcmp(argv[i], "--debug-build-verbose") == 0) {
                 verbose = true;
-                args.append(argv[i]);
             } else {
                 args.append(argv[i]);
             }

std/buf_map.zig

@@ -11,14 +11,13 @@ pub const BufMap = struct {
 
     pub fn init(allocator: &Allocator) -> BufMap {
         var self = BufMap {
-            .hash_map = undefined,
+            .hash_map = BufMapHashMap.init(allocator),
         };
-        self.hash_map.init(allocator);
         return self;
     }
 
     pub fn deinit(self: &BufMap) {
-        var it = self.hash_map.entryIterator();
+        var it = self.hash_map.iterator();
         while (true) {
             const entry = it.next() ?? break; 
             self.free(entry.key);
@@ -54,7 +53,7 @@ pub const BufMap = struct {
     }
 
     pub fn iterator(self: &const BufMap) -> BufMapHashMap.Iterator {
-        return self.hash_map.entryIterator();
+        return self.hash_map.iterator();
     }
 
     fn free(self: &BufMap, value: []const u8) {

std/buf_set.zig

@@ -9,14 +9,13 @@ pub const BufSet = struct {
 
     pub fn init(allocator: &Allocator) -> BufSet {
         var self = BufSet {
-            .hash_map = undefined,
+            .hash_map = BufSetHashMap.init(allocator),
         };
-        self.hash_map.init(allocator);
         return self;
     }
 
     pub fn deinit(self: &BufSet) {
-        var it = self.hash_map.entryIterator();
+        var it = self.hash_map.iterator();
         while (true) {
             const entry = it.next() ?? break; 
             self.free(entry.key);
@@ -43,7 +42,7 @@ pub const BufSet = struct {
     }
 
     pub fn iterator(self: &const BufSet) -> BufSetHashMap.Iterator {
-        return self.hash_map.entryIterator();
+        return self.hash_map.iterator();
     }
 
     fn free(self: &BufSet, value: []const u8) {