Unified - Add the build.info command OVERRIDE, to avoid build file clashes

Should it be needed because the recipes within a RAW section might
clash with those generated by Configure, it's possible to tell it
not to generate them with the use of OVERRIDES, for example:

    SOURCE[libfoo]=foo.c bar.c

    OVERRIDES=bar.o
    BEGINRAW[Makefile(unix)]
    bar.o: bar.c
        $(CC) $(CFLAGS) -DSPECIAL -c -o $@ $<
    ENDRAW[Makefile(unix)]

Reviewed-by: Rich Salz <rsalz@openssl.org>

2 files changed, 15 insertions, 0 deletions

diff --git a/Configurations/README b/Configurations/README
index 40875a3..5665d24 100644
--- a/Configurations/README
+++ b/Configurations/README
@@ -404,6 +404,18 @@ configuration items:
    build hoho.h: echo "/* hoho */" > hoho.h
    ENDRAW[build.ninja(unix)]
 
+Should it be needed because the recipes within a RAW section might
+clash with those generated by Configure, it's possible to tell it
+not to generate them with the use of OVERRIDES, for example:
+
+    SOURCE[libfoo]=foo.c bar.c
+    
+    OVERRIDES=bar.o
+    BEGINRAW[Makefile(unix)]
+    bar.o: bar.c
+    	$(CC) $(CFLAGS) -DSPECIAL -c -o $@ $<
+    ENDRAW[Makefile(unix)]
+
 See the documentation further up for more information on configuration
 items.
 
diff --git a/Configurations/common.tmpl b/Configurations/common.tmpl
index b97abfb..c2362d0 100644
--- a/Configurations/common.tmpl
+++ b/Configurations/common.tmpl
@@ -134,6 +134,9 @@
      $cache{$script} = 1;
  }
 
+ # Start with populating the cache with all the overrides
+ %cache = map { $_ => 1 } @{$unified_info{overrides}};
+
  # Build all known libraries, engines, programs and scripts.
  # Everything else will be handled as a consequence.
  map { dolib($_) } @{$unified_info{libraries}};