Make it possible to disable the loader_attic engine

Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/15320)

Configure

@@ -449,6 +449,7 @@ my @disablables = (
     "idea",
     "ktls",
     "legacy",
+    "loadereng",
     "makedepend",
     "md2",
     "md4",

engines/build.info

@@ -69,8 +69,19 @@ IF[{- !$disabled{"engine"} -}]
         GENERATE[devcrypto.ld]=../util/engines.num
       ENDIF
     ENDIF
+    IF[{- !$disabled{"loadereng"} -}]
+      MODULES{engine}=loader_attic
+      SOURCE[loader_attic]=e_loader_attic.c ../crypto/pem/pvkfmt.c
+      DEFINE[loader_attic]=OPENSSL_NO_PROVIDER_CODE
+      DEPEND[loader_attic]=../libcrypto
+      INCLUDE[loader_attic]=../include
+      IF[{- defined $target{shared_defflag} -}]
+        SOURCE[loader_attic]=loader_attic.ld
+        GENERATE[loader_attic.ld]=../util/engines.num
+      ENDIF
+    ENDIF
 
-    MODULES{noinst,engine}=ossltest dasync loader_attic
+    MODULES{noinst,engine}=ossltest dasync
     SOURCE[dasync]=e_dasync.c
     DEPEND[dasync]=../libcrypto
     INCLUDE[dasync]=../include
@@ -86,15 +97,6 @@ IF[{- !$disabled{"engine"} -}]
       SOURCE[ossltest]=ossltest.ld
       GENERATE[ossltest.ld]=../util/engines.num
     ENDIF
-
-    SOURCE[loader_attic]=e_loader_attic.c ../crypto/pem/pvkfmt.c
-    DEFINE[loader_attic]=OPENSSL_NO_PROVIDER_CODE
-    DEPEND[loader_attic]=../libcrypto
-    INCLUDE[loader_attic]=../include
-    IF[{- defined $target{shared_defflag} -}]
-      SOURCE[loader_attic]=loader_attic.ld
-      GENERATE[loader_attic.ld]=../util/engines.num
-    ENDIF
   ENDIF
   GENERATE[e_padlock-x86.s]=asm/e_padlock-x86.pl
   GENERATE[e_padlock-x86_64.s]=asm/e_padlock-x86_64.pl