Add PyPy v7.3.20 (#3284)

The release blog entry is here:
  https://pypy.org/posts/2025/07/pypy-v7320-release.html

plugins/python-build/share/python-build/pypy3.11-7.3.20

@@ -0,0 +1,77 @@
+VERSION='7.3.20'
+PYVER='3.11'
+
+# https://www.pypy.org/checksums.html
+aarch64_hash=9347fe691a07fd9df17a1b186554fb9d9e6210178ffef19520a579ce1f9eb741
+linux32_hash=d08ce15dd61e9ace5e010b047104f0137110a258184e448ea8239472f10cf99b
+linux64_hash=1410db3a7ae47603e2b7cbfd7ff6390b891b2e041c9eb4f1599f333677bccb3e
+osarm64_hash=84a48e09c97f57df62cc9f01b7a6d8c3e306b6270671d871aa8ab8c06945940d
+osx64_hash=bb3ae80cf5fca5044af2e42933e7692c7c5e76a828ce0eb6404a5d5da83b313c
+
+### end of manual settings - following lines same for every download
+
+function err_no_binary {
+    local archmsg="${1}"
+    local ver="pypy${PYVER}-v${VERSION}-src"
+    local url="https://downloads.python.org/pypy/${ver}.tar.bz2"
+    { echo
+      colorize 1 "ERROR"
+      echo ": The binary distribution of PyPy is not available for ${archmsg}."
+      echo "try '${url}' to build from source."
+      echo
+    } >&2
+    exit 1
+}
+
+function pypy_pkg_data {
+    # pypy architecture tag
+    local ARCH="${1}"
+
+    # defaults
+    local cmd='install_package'  # use bz2
+    local pkg="${ARCH}" # assume matches
+    local ext='tar.bz2'
+    local hash='' # undefined
+
+    # select the hash, fix pkg if not match ARCH
+    case "${ARCH}" in
+    'linux-aarch64' )
+      hash="${aarch64_hash}"
+      pkg='aarch64'
+      ;;
+    'linux' )
+      hash="${linux32_hash}"
+      pkg='linux32'
+      ;;
+    'linux64' )
+      hash="${linux64_hash}"
+      ;;
+    'osarm64' )
+      hash="${osarm64_hash}"
+      pkg='macos_arm64'
+      ;;
+    'osx64' )
+      if require_osx_version "10.13"; then
+        hash="${osx64_hash}"
+        pkg='macos_x86_64'
+      else
+        err_no_binary "${ARCH}, OS X < 10.13"
+      fi
+      ;;
+    * )
+      err_no_binary "${ARCH}"
+      ;;
+    esac
+
+    local basever="pypy${PYVER}-v${VERSION}"
+    local baseurl="https://downloads.python.org/pypy/${basever}"
+
+    # result - command, package dir, url+hash
+    echo "${cmd}" "${basever}-${pkg}" "${baseurl}-${pkg}.${ext}#${hash}"
+}
+
+# determine command, package directory, url+hash
+declare -a pd="$(pypy_pkg_data "$(pypy_architecture 2>/dev/null || true)")"
+
+# install
+${pd[0]} "${pd[1]}" "${pd[2]}" 'pypy' "verify_py${PYVER//./}" 'ensurepip'