BLD Add DISTDIR variable. ### Description

Adds `DISTDIR` env variable that points to the directory where libraries should be copied to when building shared libraries with recipe.

### Checklists

- [x] Add new / update outdated documentation

package:
  name: sqlite3
  version: 1.0.0 # Nonsense
  tag:
    - always
  top-level:
    - sqlite3
    - _sqlite3
build:
  type: cpython_module
  script: |
    mkdir dist
    export DISTDIR=$(pwd)/dist
    cd $CPYTHONBUILD

    export FILES=(
      "Modules/_sqlite/blob.c"
      "Modules/_sqlite/connection.c"
      "Modules/_sqlite/cursor.c"
      "Modules/_sqlite/microprotocols.c"
      "Modules/_sqlite/module.c"
      "Modules/_sqlite/prepare_protocol.c"
      "Modules/_sqlite/row.c"
      "Modules/_sqlite/statement.c"
      "Modules/_sqlite/util.c"
    )

    embuilder build --pic sqlite3

    for file in "${FILES[@]}"; do
      emcc $STDLIB_MODULE_CFLAGS -c "${file}" -o "${file/.c/.o}"  \
        -sUSE_SQLITE3 -DMODULENAME=sqlite
    done

    OBJECT_FILES=$(find Modules/_sqlite/ -name "*.o")
    emcc $OBJECT_FILES -o $DISTDIR/_sqlite3.so $SIDE_MODULE_LDFLAGS \
       -sUSE_SQLITE3 -lsqlite3

    cd Lib && tar --exclude=test -cf - sqlite3 | tar -C $DISTDIR -xf -

package:
  name: sqlite3
  version: 1.0.0 # Nonsense
  tag:
    - always
  top-level:
    - sqlite3
    - _sqlite3
build:
  type: cpython_module
  script: |
    cd $CPYTHONBUILD

    export FILES=(
      "Modules/_sqlite/blob.c"
      "Modules/_sqlite/connection.c"
      "Modules/_sqlite/cursor.c"
      "Modules/_sqlite/microprotocols.c"
      "Modules/_sqlite/module.c"
      "Modules/_sqlite/prepare_protocol.c"
      "Modules/_sqlite/row.c"
      "Modules/_sqlite/statement.c"
      "Modules/_sqlite/util.c"
    )

    embuilder build --pic sqlite3

    for file in "${FILES[@]}"; do
      emcc $STDLIB_MODULE_CFLAGS -c "${file}" -o "${file/.c/.o}"  \
        -sUSE_SQLITE3 -DMODULENAME=sqlite
    done

    OBJECT_FILES=$(find Modules/_sqlite/ -name "*.o")
    emcc $OBJECT_FILES -o $DISTDIR/_sqlite3.so $SIDE_MODULE_LDFLAGS \
       -sUSE_SQLITE3 -lsqlite3

    cd Lib && tar --exclude=test -cf - sqlite3 | tar -C $DISTDIR -xf -
