build: Fix recent commit for SOURCE_DATE_EPOCH.

--

Fixes-commit: 074ab108e7
which was recently pushed to make use of $SOURCE_DATE_EPOCH
as fallback.

Also fixes two typos

Makefile.am

@@ -20,7 +20,7 @@
 
 # Location of the released tarball archives.  Note that this is an
 # internal archive and before uploading this to the public server,
-# manual tests should be run and the git release tat set and pushed.
+# manual tests should be run and the git release tag set and pushed.
 # Adjust as needed.
 RELEASE_ARCHIVE_DIR  = wk@vigenere:tarballs/gnupg/v2.2
 

doc/Makefile.am

@@ -177,8 +177,8 @@ defsincdate: $(gnupg_TEXINFOS)
 	if test -e $(top_srcdir)/.git; then \
 	  (cd $(srcdir) && git log -1 --format='%ct' \
                -- $(gnupg_TEXINFOS) 2>/dev/null) >>defsincdate; \
-        elif test x"$SOURCE_DATE_EPOCH" != x; then   \
-	   echo "$SOURCE_DATE_EPOCH" >>defsincdate ; \
+        elif test x"$$SOURCE_DATE_EPOCH" != x; then   \
+	   echo "$$SOURCE_DATE_EPOCH" >>defsincdate ; \
 	fi
 
 defs.inc : defsincdate Makefile mkdefsinc

scd/app-piv.c

@@ -1180,7 +1180,7 @@ do_learn_status (app_t app, ctrl_t ctrl, unsigned int flags)
  * R_CERT and the length of the certificate stored at R_CERTLEN.  If
  * on success a non-zero value is stored at R_MECHANISM, the returned
  * data is not a certificate but a public key (in the format used by the
- * container '7f49'.  */
+ * container '7f49').  */
 static gpg_error_t
 readcert_by_tag (app_t app, unsigned int tag,
                  unsigned char **r_cert, size_t *r_certlen, int *r_mechanism)