Give SQLITE_VEC_API no __attribute__ under MSVC in static builds

CHANGELOG.md

@@ -8,6 +8,7 @@
 
 ### Fixed
 
+- Compiling `sqlite-vec.c` with MSVC and `-DSQLITE_VEC_STATIC` succeeds; in that build `sqlite-vec.h` declared `sqlite3_vec_init()` with `__attribute__((visibility("default")))` on every compiler, and MSVC, which has no `__attribute__`, stopped with `error C2143`. GCC and Clang builds are unchanged.
 - A KNN query that takes its query vector, `k`, or `mmr_lambda` from another table of a join now uses it. `select v.rowid from p join v on v.embedding match ? and v.k = p.k` failed with `A LIMIT or 'k = ?' constraint is required`; the same join with `v.k = 3 and v.mmr_lambda = p.lambda` returned no rows; and `select v.rowid from v join p on p.id = v.tag where v.embedding match p.vector and v.k = 2`, with `p.id` an integer primary key, could return no rows. These joins now run one KNN per row of the other table, so a filter on the `vec0` table whose value comes from that table applies before the k nearest rows are chosen. Ported in part from the unmerged [vlasky#14](https://github.com/vlasky/sqlite-vec/pull/14) ([asg017#331](https://github.com/asg017/sqlite-vec/pull/331)), which also applies filters whose value comes from a joined table before the k nearest rows are chosen; that part is not ported, and ARCHITECTURE.md's idxStr section says why.
 
 ## [2.1.1] - 2026-10-09

sqlite-vec.h.tmpl

@@ -8,8 +8,12 @@
 #endif
 
 #ifdef SQLITE_VEC_STATIC
+#if defined(__GNUC__) && !defined(_WIN32)
 #define SQLITE_VEC_API __attribute__((visibility("default")))
 #else
+#define SQLITE_VEC_API
+#endif
+#else
 #ifdef _WIN32
 #define SQLITE_VEC_API __declspec(dllexport)
 #else