Bugfix: Only install manpages for built programs

Author: luke-jr

doc/man/Makefile.am

@@ -1 +1,13 @@
-dist_man1_MANS=bitcoind.1 bitcoin-qt.1 bitcoin-cli.1 bitcoin-tx.1
+dist_man1_MANS=
+
+if BUILD_BITCOIND
+  dist_man1_MANS+=bitcoind.1
+endif
+
+if ENABLE_QT
+  dist_man1_MANS+=bitcoin-qt.1
+endif
+
+if BUILD_BITCOIN_UTILS
+  dist_man1_MANS+=bitcoin-cli.1 bitcoin-tx.1
+endif