Add ability to disable use of preprocessed output in compilation

This can be done from a buildfile for a scope (including project root scope)
and per target via cc.reprocess:

cc.reprocess = true
obj{hello}: cc.reprocess = false

As as well externally via config.cc.reprocess:

b config.cc.reprocess=true [configure]

1 files changed, 8 insertions, 0 deletions

diff --git a/build2/cc/init.cxx b/build2/cc/init.cxx
index 8d20573..a5fcf83 100644
--- a/build2/cc/init.cxx
+++ b/build2/cc/init.cxx
@@ -78,6 +78,11 @@ namespace build2
       //
       v.insert<bool> ("cc.system");
 
+      // Ability to disable using preprocessed output for compilation.
+      //
+      v.insert<bool> ("config.cc.reprocess", true);
+      v.insert<bool> ("cc.reprocess");
+
       return true;
     }
 
@@ -166,6 +171,9 @@ namespace build2
       rs.assign ("cc.libs") += cast_null<strings> (
         config::optional (rs, "config.cc.libs"));
 
+      if (lookup l = config::omitted (rs, "config.cc.reprocess").first)
+        rs.assign ("cc.reprocess") = *l;
+
       // Load the bin.config module.
       //
       if (!cast_false<bool> (rs["bin.config.loaded"]))