vccenv module for vcc auto-discovery

Only works for VCC Installations with Visual Studio 2015 and below

tools/vccexe/vccenv.nim

@@ -0,0 +1,25 @@
+import os
+
+type
+  VccEnvVersion* = enum
+    vsUndefined = (0, ""),
+    vs90  = (90,   "VS90COMNTOOLS"), # Visual Studio 2008
+    vs100 = (100, "VS100COMNTOOLS"), # Visual Studio 2010
+    vs110 = (110, "VS110COMNTOOLS"), # Visual Studio 2012
+    vs120 = (120, "VS120COMNTOOLS"), # Visual Studio 2013
+    vs140 = (140, "VS140COMNTOOLS")  # Visual Studio 2015
+
+const
+  vcvarsallRelativePath = joinPath("..", "..", "VC", "vcvarsall")
+
+proc vccEnvVcVarsAllPath*(version: VccEnvVersion = vsUndefined): string =
+  if version == vsUndefined:
+    for tryVersion in [vs140, vs120, vs110, vs100, vs90]:
+      let tryPath = vccEnvVcVarsAllPath(tryVersion)
+      if tryPath.len > 0:
+        result = tryPath
+  else: # Specific version requested
+    let key = $version
+    let val = getEnv key
+    if val.len > 0:
+      result = expandFilename(val & vcvarsallRelativePath)