Extend legacy_stdio_definitions.lib by _[v]snprintf

Wrt. ldc-developers/ldc#3212; these 2 legacy functions have slightly
different semantics than standard [v]snprintf.

Also enable optimizations for these printf/scanf functions (mostly
forwarding one-liners); they are apparently all still emitted into the
object file.

Author: kinke

buildsdk.d

@@ -336,11 +336,11 @@ bool defWithStdcallMangling2implib(string defFile)
     return true;
 }
 
-void c2lib(string outDir, string cFile)
+void c2lib(string outDir, string cFile, string clFlags = null)
 {
     const obj = buildPath(outDir, baseName(cFile).setExtension(".obj"));
     const lib = setExtension(obj, ".lib");
-    cl(obj, quote(cFile));
+    cl(obj, clFlags ? clFlags ~ " " ~ quote(cFile) : quote(cFile));
     runShell(`lib "/OUT:` ~ lib ~ `" ` ~ quote(obj));
     std.file.remove(obj);
 }
@@ -431,7 +431,7 @@ void buildOldnames(string outDir)
 
 void buildLegacyStdioDefinitions(string outDir)
 {
-    c2lib(outDir, "legacy_stdio_definitions.c");
+    c2lib(outDir, "legacy_stdio_definitions.c", "/O2");
 }
 
 // create empty uuid.lib (expected by dmd, but UUIDs already in druntime)

legacy_stdio_definitions.c

@@ -15,6 +15,7 @@ void __legacy_stdio_definitions()
     printf(NULL);
     scanf(NULL);
     snprintf(NULL, 0, NULL);
+    _snprintf(NULL, 0, NULL);
     sprintf(NULL, NULL);
     sscanf(NULL, NULL);
     swprintf(NULL, 0, NULL);
@@ -26,6 +27,7 @@ void __legacy_stdio_definitions()
     vprintf(NULL, NULL);
     vscanf(NULL, NULL);
     vsnprintf(NULL, 0, NULL, NULL);
+    _vsnprintf(NULL, 0, NULL, NULL);
     vsprintf(NULL, NULL, NULL);
     vsscanf(NULL, NULL, NULL);
     vswprintf(NULL, 0, NULL, NULL);
@@ -34,4 +36,4 @@ void __legacy_stdio_definitions()
     vwscanf(NULL, NULL);
     wprintf(NULL);
     wscanf(NULL);
-}
+}