From Thunderbird 78 there are more NSS tools built and they require to
remove some old workarounds.

To be investigated and sent to NSS upstream.

--- thunderbird-78.0/security/nss/cmd/btoa/btoa.c
+++ thunderbird-78.0/security/nss/cmd/btoa/btoa.c
@@ -7,13 +7,11 @@
 #include "nssb64.h"
 #include <errno.h>
 
-#if defined(XP_WIN) || (defined(__sun) && !defined(SVR4))
-#if !defined(WIN32)
+#if defined(XP_WIN) && !defined(WIN32)
 extern int fread(char *, size_t, size_t, FILE *);
 extern int fwrite(char *, size_t, size_t, FILE *);
 extern int fprintf(FILE *, char *, ...);
 #endif
-#endif
 
 #if defined(WIN32)
 #include "fcntl.h"
--- thunderbird-78.0/security/nss/cmd/atob/atob.c
+++ thunderbird-78.0/security/nss/cmd/atob/atob.c
@@ -7,13 +7,11 @@
 #include "nssb64.h"
 #include <errno.h>
 
-#if defined(XP_WIN) || (defined(__sun) && !defined(SVR4))
-#if !defined(WIN32)
+#if defined(XP_WIN) && !defined(WIN32)
 extern int fread(char *, size_t, size_t, FILE *);
 extern int fwrite(char *, size_t, size_t, FILE *);
 extern int fprintf(FILE *, char *, ...);
 #endif
-#endif
 
 #if defined(WIN32)
 #include "fcntl.h"