djgpp: Skip test/rsa_complex.c

We don't have <complex.h> on djgpp, so this entire test can be skipped.
Reviewed-by: NRichard Levitte <levitte@openssl.org>
Reviewed-by: NHugo Landau <hlandau@openssl.org>
Reviewed-by: NTomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/19286)

test/rsa_complex.c

@@ -11,13 +11,18 @@
  * Check to see if there is a conflict between complex.h and openssl/rsa.h.
  * The former defines "I" as a macro and earlier versions of the latter use
  * for function arguments.
+ *
+ * Will always succeed on djgpp, since its libc does not have complex.h.
  */
-#if defined(__STDC_VERSION__)
-# if __STDC_VERSION__ >= 199901L
-#  include <complex.h>
+
+#if !defined(__DJGPP__)
+# if defined(__STDC_VERSION__)
+#  if __STDC_VERSION__ >= 199901L
+#   include <complex.h>
+#  endif
 # endif
+# include <openssl/rsa.h>
 #endif
-#include <openssl/rsa.h>
 #include <stdlib.h>
 
 int main(int argc, char *argv[])