Avoid "multiple definition of `mystruct'" error from `ld`:

Submitted upstream at https://github.com/idris-lang/Idris-dev/issues/4914

--- a/test/ffi008/ffi008.h	1969-12-31 18:00:01.000000000 -0600
+++ a/test/ffi008/ffi008.h	2022-04-13 00:32:35.561262598 -0500
@@ -10,7 +10,7 @@
     int16_t b;
 };
 
-struct test2 mystruct;
+extern struct test2 mystruct;
 
 int size1(void);
 int size2(void);
--- a/test/ffi008/ffi008.c	1969-12-31 18:00:01.000000000 -0600
+++ a/test/ffi008/ffi008.c	2022-04-13 00:32:53.145186302 -0500
@@ -11,6 +11,8 @@
     return sizeof(struct test2);
 }
 
+struct test2 mystruct;
+
 void print_mystruct(void) {
     printf("a: %d b: %d\n", mystruct.a, mystruct.b);
 }
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<tr><td><span title='2021-12-22 10:53:19 +0100'>2021-12-22</span></td><td><a href='/guix/commit/tests/keys/ed25519.sec?id=9ebc9ca070a21ba0aeb3f61202a8071bb250ccc8'>tests: Move keys into ./tests/keys/ and add a third ed25519 key.</a><span class='msg-avail'>...<span class='msg-tooltip'>The third key will be used in an upcoming commit.

Rename public keys to .pub.

* guix/tests/gnupg.scm (%ed25519-3-public-key-file): New variable.
(%ed25519-3-secret-key-file): New variable.
(%ed25519-2-public-key-file): Renamed from %ed25519bis-public-key-file.
(%ed25519-2-secret-key-file): Renamed from %ed25519bis-secret-key-file.
* tests/keys/ed25519-3.key: New file.
* tests/keys/ed25519-3.sec: New file.

Signed-off-by: Mathieu Othacehe &lt;othacehe@gnu.org&gt;
</span></span></td><td>Attila Lendvai</td></tr>