dev-libs/libxml2: Revert "Fix cross-compilation with USE=python"

- Attempted soultion was wrong because the script executes Python at a
  given path which can't work if it was compiled for a different
  architecture.

This reverts commit 7963aaf058.

Bug: https://bugs.gentoo.org/582130
Signed-off-by: Jakov Smolić <jsmolic@gentoo.org>

dev-libs/libxml2/libxml2-2.9.12-r5.ebuild

@@ -165,7 +165,7 @@ multilib_src_configure() {
 
 		# Odd build system, also see bug #582130
 		run_in_build_dir libxml2_configure \
-			"--with-python=${ESYSROOT}/${PYTHON}"
+			"--with-python=${EPYTHON}" \
 			"--with-python-install-dir=$(python_get_sitedir)"
 	}