Fix Windows build: pass --no-keep-memory to linker for large DuckDB lib

MinGW's ld runs out of memory linking DuckDB's large static library.
The --no-keep-memory flag reduces ld's memory usage at the cost of
slower linking.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: wesm

.github/workflows/release.yml

@@ -167,7 +167,7 @@ jobs:
           $VERSION = "${{ github.ref_name }}".TrimStart("v")
 
           New-Item -ItemType Directory -Force -Path dist | Out-Null
-          $LDFLAGS = "-s -w -X github.com/wesm/msgvault/cmd/msgvault/cmd.Version=v${VERSION}"
+          $LDFLAGS = "-s -w -X github.com/wesm/msgvault/cmd/msgvault/cmd.Version=v${VERSION} -extldflags '-Wl,--no-keep-memory'"
           go build -tags fts5 -trimpath -ldflags="$LDFLAGS" -o dist/msgvault.exe ./cmd/msgvault
           if ($LASTEXITCODE -ne 0) { throw "Build failed" }