Move Trusty workaround to the OPENSSL_LINUX define.

See b/169780122. This CL should be a no-op (the only other OPENSSL_LINUX
defines are in urandom/getrandom logic, which Trusty doesn't use), but
should be easier to work for future code.

Change-Id: I7676ce234a20ddaf54a881f2da1e1fcd680d1c78
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/43224
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: David Benjamin <davidben@google.com>

crypto/fipsmodule/rand/fork_detect.c

@@ -20,7 +20,7 @@
 
 #include "fork_detect.h"
 
-#if defined(OPENSSL_LINUX) && !defined(OPENSSL_TRUSTY)
+#if defined(OPENSSL_LINUX)
 #include <sys/mman.h>
 #include <unistd.h>
 #include <stdlib.h>

include/openssl/base.h

@@ -138,7 +138,10 @@ extern "C" {
 #define OPENSSL_WINDOWS
 #endif
 
-#if defined(__linux__)
+// Trusty isn't Linux but currently defines __linux__. As a workaround, we
+// exclude it here.
+// TODO(b/169780122): Remove this workaround once Trusty no longer defines it.
+#if defined(__linux__) && !defined(TRUSTY)
 #define OPENSSL_LINUX
 #endif