Unified build: Keep track of generated header files

If someone runs a mixed unixmake / unified environment (the unified
build tree would obviously be out of the source tree), the unified
build will pick up on the unixmake crypto/buildinf.h because of
assumptions made around this sort of declaration (found in
crypto/build.info):

    DEPENDS[cversion.o]=buildinf.h

The assumption was that if such a header could be found in the source
tree, that was the one to depend on, otherwise it would assume it
should be in the build tree.

This change makes sure that sort of mix-up won't happen again.
Reviewed-by: NRich Salz <rsalz@openssl.org>

Configure

@@ -395,6 +395,15 @@ my @default_depdefines =
 # We will collect such requests in @experimental.
 # To avoid accidental use of experimental features, applications will have to use -DOPENSSL_EXPERIMENTAL_FOO.
 
+my @generated_headers = (
+    "include/openssl/opensslconf.h",
+    "crypto/include/internal/bn_conf.h"
+    );
+
+my @generated_by_make_headers = (
+    "crypto/buildinf.h"
+    );
+
 
 my $no_sse2=0;
 
@@ -1481,9 +1490,15 @@ EOF
             foreach (@{$depends{$dest}}) {
                 my $d = cleanfile($sourced, $_, $blddir);
 
-                # If it isn't found in the source, let's assume it's generated
-                # and that the Makefile template has the lines
-                if (! -f $d) {
+                # If we know it's generated, or assume it is because we can't
+                # find it in the source tree, we set file we depend on to be
+                # in the build tree rather than the source tree, and assume
+                # and that there are lines to build it in a BEGINRAW..ENDRAW
+                # section or in the Makefile template.
+                if (! -f $d
+                    || !(grep { $d eq $_ }
+                         map { cleanfile($srcdir, $_, $blddir) }
+                         (@generated_headers, @generated_by_make_headers))) {
                     $d = cleanfile($buildd, $_, $blddir);
                 }
                 # Take note if the file to depend on is being renamed
@@ -1697,14 +1712,10 @@ print "THIRTY_TWO_BIT mode\n" if $config{b32};
 print "BN_LLONG mode\n" if $config{bn_ll};
 print "RC4 uses $config{rc4_int}\n" if $config{rc4_int} != $def_int;
 
-mkpath(catdir($blddir, "include/openssl"));
-run_dofile(catfile($blddir, "include/openssl/opensslconf.h"),
-           catfile($srcdir, "include/openssl/opensslconf.h.in"));
-
-mkpath(catdir($blddir, "crypto/include/internal"));
-foreach my $alg ( 'bn' ) {
-    run_dofile(catfile($blddir, "crypto/include/internal/${alg}_conf.h"),
-               catfile($srcdir, "crypto/include/internal/${alg}_conf.h.in"));
+for (@generated_headers) {
+    mkpath(catdir($blddir, dirname($_)));
+    run_dofile(catfile($blddir, $_),
+               catfile($srcdir, $_.".in"));
 }
 
 ###