Packages the distutils stdlib module as a standalone package,
```
377K distutils.data
221K distutils.data.br
19K distutils.js
```
to reduce the minimal pyodide size.

Part of #1542 

This also,
 - adds documentation on what's supported or not in the stdlib
 - makes a few changes to `pyodide_build/buildall.py` to be able to add such stdlib packages as a dependency in other packages (which didn't work before). For instance, until there is a release with https://github.com/pypa/packaging/pull/396 micropip has a dependency on distutils.
Unvendor distutils. Packages the distutils stdlib module as a standalone package,
```
377K distutils.data
221K distutils.data.br
19K distutils.js
```
to reduce the minimal pyodide size.

Part of #1542 

This also,
 - adds documentation on what's supported or not in the stdlib
 - makes a few changes to `pyodide_build/buildall.py` to be able to add such stdlib packages as a dependency in other packages (which didn't work before). For instance, until there is a release with https://github.com/pypa/packaging/pull/396 micropip has a dependency on distutils.
package:
  name: libiconv
  version: "1.16"

source:
  url: https://ftp.gnu.org/pub/gnu/libiconv/libiconv-1.16.tar.gz
  sha256: e6a1b1b589654277ee790cce3734f07876ac4ccfaecbee8afa0b649cf529cc04

build:
  library: true
  script: |
    emconfigure ./configure \
       CFLAGS="-fPIC" \
       --disable-dependency-tracking \
       --disable-shared
    emmake make -j ${PYODIDE_JOBS:-3}

package:
  name: libiconv
  version: "1.16"

source:
  url: https://ftp.gnu.org/pub/gnu/libiconv/libiconv-1.16.tar.gz
  sha256: e6a1b1b589654277ee790cce3734f07876ac4ccfaecbee8afa0b649cf529cc04

build:
  library: true
  script: |
    emconfigure ./configure \
       CFLAGS="-fPIC" \
       --disable-dependency-tracking \
       --disable-shared
    emmake make -j ${PYODIDE_JOBS:-3}
