Bring back bld with new design

build.cpp

@@ -0,0 +1,28 @@
+#include "bld_lib.cpp"
+
+int Main() {
+    bool debug = true;
+    bool release = !debug;
+    bool use_std = false;
+
+    Strs cc = "cl.exe";
+    Strs flags = Split("-WX -W3 -wd4200 -diagnostics:column -nologo -Z7 -FC -GF -Gm- -Oi -Zo -D_CRT_SECURE_NO_WARNINGS");
+    Strs link = Split("-link -incremental:no");
+    Strs files = Split("../test/main_core_as_header.cpp");
+    files += IfCodeWasModified("../core.c", "../core.obj");
+    if (use_std) {
+        flags += Split("-GR- -EHa-");
+    }
+    if (!use_std) {
+        flags += Split("-EHsc");
+    }
+    if (release) {
+        flags += Split("-O2 -MT -DNDEBUG -GL");
+        link += Split("-opt:ref -opt:icf -ltcg");
+    }
+    if (debug) {
+        flags += Split("-Od -D_DEBUG -MTd -fsanitize=address -MTd -RTC1");
+        link += Split("-NODEFAULTLIB:LIBCMT");
+    }
+    return Run(cc + files + flags + link);
+}