Fixes iOS build failures caused by linker picking up macOS SQLite
libraries from pkgx instead of iOS system SQLite, resulting in
undefined symbol errors for all sqlite3 functions.
Changes:
- Explicitly link system SQLite library (-lsqlite3) in podspec
- Detect and unset pkgx environment variables during iOS builds
- Add warnings to guide users if manual intervention needed
The issue occurs when pkgx (or similar package managers) set
DYLD_LIBRARY_PATH or PKGX_DIR, causing the linker to find macOS
SQLite dylibs at /Users/*/.pkgx/sqlite.org/*/lib/libsqlite3.0.dylib
instead of the iOS system SQLite library.
This fix ensures the iOS build always uses the correct system SQLite
library regardless of environment variable interference.
630fd3de81