bpo-30342: Fix sysconfig.is_python_build() on VS9.0 (#1544)

Fix sysconfig.is_python_build() if Python is built with Visual Studio
2008 (VS 9.0).
diff --git a/Lib/sysconfig.py b/Lib/sysconfig.py
index 2a1da5a..9c8350d 100644
--- a/Lib/sysconfig.py
+++ b/Lib/sysconfig.py
@@ -112,6 +112,11 @@
 # PC/VS7.1
 if os.name == "nt" and "\\pc\\v" in _PROJECT_BASE[-10:].lower():
     _PROJECT_BASE = _safe_realpath(os.path.join(_PROJECT_BASE, pardir, pardir))
+# PC/VS9.0/amd64
+if (os.name == "nt"
+   and os.path.basename(os.path.dirname(os.path.dirname(_PROJECT_BASE))).lower() == "pc"
+   and os.path.basename(os.path.dirname(_PROJECT_BASE)).lower() == "vs9.0"):
+    _PROJECT_BASE = _safe_realpath(os.path.join(_PROJECT_BASE, pardir, pardir, pardir))
 # PC/AMD64
 if os.name == "nt" and "\\pcbuild\\amd64" in _PROJECT_BASE[-14:].lower():
     _PROJECT_BASE = _safe_realpath(os.path.join(_PROJECT_BASE, pardir, pardir))