llvmjit: Make llvm_types_module variable static

Commit b059d2f456 introduced llvm_types_module and accidentally
exported it. As there is no usecase for accessing this variable
externally, this makes it static.

Author: Andres Freund <andres@anarazel.de>
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Discussion: https://postgr.es/m/20221101055132.pjjsvlkeo4stbjkq@awork3.anarazel.de

src/backend/jit/llvm/llvmjit.c

@@ -77,7 +77,7 @@ LLVMTypeRef StructAggStatePerTransData;
 
 LLVMValueRef AttributeTemplate;
 
-LLVMModuleRef llvm_types_module = NULL;
+static LLVMModuleRef llvm_types_module = NULL;
 
 static bool llvm_session_initialized = false;
 static size_t llvm_generation = 0;

src/include/jit/llvmjit.h

@@ -55,9 +55,6 @@ typedef struct LLVMJitContext
 	List	   *handles;
 } LLVMJitContext;
 
-/* llvm module containing information about types */
-extern PGDLLIMPORT LLVMModuleRef llvm_types_module;
-
 /* type and struct definitions */
 extern PGDLLIMPORT LLVMTypeRef TypeParamBool;
 extern PGDLLIMPORT LLVMTypeRef TypePGFunction;