findpython: set PDM_PEP517_SCM_VERSION

so pdm knows the package version without git

mingw-w64-python-findpython/PKGBUILD

@@ -4,7 +4,7 @@ _realname=findpython
 pkgbase=mingw-w64-python-${_realname}
 pkgname=("${MINGW_PACKAGE_PREFIX}-python-${_realname}")
 pkgver=0.2.5
-pkgrel=1
+pkgrel=2
 pkgdesc='A utility to find python versions on your system (mingw-w64)'
 arch=('any')
 mingw_arch=('mingw32' 'mingw64' 'ucrt64' 'clang64' 'clang32' 'clangarm64')
@@ -23,6 +23,8 @@ sha256sums=('be1b3833fb6ee53086a5ffc1f0203f7289313f7dcf15060f47bef38a490e1c54')
 build() {
   cp -r "${_realname}-${pkgver}" "python-build-${MSYSTEM}" && cd "python-build-${MSYSTEM}"
 
+  export PDM_PEP517_SCM_VERSION=${pkgver}
+
   ${MINGW_PREFIX}/bin/python -m build --wheel --skip-dependency-check --no-isolation
 }