Your script does this for non-debug builds:
```
export CFLAGS="-fPIC \
```
but does this for debug builds:
```
export SQLITE3_CFLAGS="-fPIC \
```
hence my original comment.
> The C compiler expects CFLAGS.
Most (all?) C compilers ignore `CFLAGS`, as they expect build flags on the command line. It's the `configure` script that captures the value of `CFLAGS` and modifies the various build control files accordingly.