Starting to split up alloy/core.h.

src/alloy/hir/hir_builder.h

@@ -10,6 +10,8 @@
 #ifndef ALLOY_HIR_HIR_BUILDER_H_
 #define ALLOY_HIR_HIR_BUILDER_H_
 
+#include <vector>
+
 #include <alloy/core.h>
 #include <alloy/hir/block.h>
 #include <alloy/hir/instr.h>
@@ -17,6 +19,10 @@
 #include <alloy/hir/opcodes.h>
 #include <alloy/hir/value.h>
 
+namespace alloy {
+class StringBuffer;
+}  // namespace alloy
+
 namespace alloy {
 namespace hir {