Fix error maybe-uninitialized (#2230)

* Add build instructions for Arch Linux

* Fix error maybe-uninitialized in llvm_codegen_expr.c when compiling with clang 20.1.6

README.md

@@ -379,8 +379,7 @@ The c3c binary should be created in the build directory. You can try it out by r
 ```bash
 cmake -B build \
     -D C3_LINK_DYNAMIC=ON \
-    -D CMAKE_BUILD_TYPE=Release \
-    -D CMAKE_C_FLAGS_RELEASE="-Wno-error=maybe-uninitialized"
+    -D CMAKE_BUILD_TYPE=Release
 ```
 5. Build the project: `make -C build`.
 

src/compiler/llvm_codegen_expr.c

@@ -2051,7 +2051,7 @@ static inline LLVMValueRef llvm_emit_inc_dec_value(GenContext *c, SourceSpan spa
 			Type *element = type_lowering(type->array.base);
 			LLVMValueRef diff_value;
 			bool is_integer = type_kind_is_any_integer(element->type_kind);
-			bool is_ptr;
+			bool is_ptr = false;
 			if (is_integer)
 			{
 				diff_value = LLVMConstInt(llvm_get_type(c, element), 1, false);