build: Remove unnecessary executables from gitian release

This removes the following executables from the binary gitian release:

- test_bitcoin-qt[.exe]
- bench_bitcoin[.exe]

@jonasschnelli and me discussed this on IRC a few days ago - unlike the
normal `bitcoin_tests` which is useful to see if it is safe to run
bitcoin on a certain OS/environment combination, there is no good reason
to include these. Better to leave them out to reduce the download
size.

Sizes from the 0.12 release:
```
2.4M bitcoin-0.12.0/bin/bench_bitcoin.exe
 22M bitcoin-0.12.0/bin/test_bitcoin-qt.exe
```

configure.ac

@@ -97,6 +97,11 @@ AC_ARG_ENABLE(tests,
     [use_tests=$enableval],
     [use_tests=yes])
 
+AC_ARG_ENABLE(gui-tests,
+    AS_HELP_STRING([--disable-gui-tests],[do not compile GUI tests (default is to compile if GUI and tests enabled)]),
+    [use_gui_tests=$enableval],
+    [use_gui_tests=$use_tests])
+
 AC_ARG_WITH([comparison-tool],
     AS_HELP_STRING([--with-comparison-tool],[path to java comparison tool (requires --enable-tests)]),
     [use_comparison_tool=$withval],
@@ -811,8 +816,8 @@ else
 fi
 
 dnl these are only used when qt is enabled
+BUILD_TEST_QT=""
 if test x$bitcoin_enable_qt != xno; then
-  BUILD_QT=qt
   dnl enable dbus support
   AC_MSG_CHECKING([whether to build GUI with support for D-Bus])
   if test x$bitcoin_enable_qt_dbus != xno; then
@@ -842,9 +847,9 @@ if test x$bitcoin_enable_qt != xno; then
   fi
 
   AC_MSG_CHECKING([whether to build test_bitcoin-qt])
-  if test x$use_tests$bitcoin_enable_qt_test = xyesyes; then
+  if test x$use_gui_tests$bitcoin_enable_qt_test = xyesyes; then
     AC_MSG_RESULT([yes])
-    BUILD_TEST_QT="test"
+    BUILD_TEST_QT="yes"
   else
     AC_MSG_RESULT([no])
   fi
@@ -853,9 +858,10 @@ fi
 AC_MSG_CHECKING([whether to build test_bitcoin])
 if test x$use_tests = xyes; then
   AC_MSG_RESULT([yes])
-  BUILD_TEST="test"
+  BUILD_TEST="yes"
 else
   AC_MSG_RESULT([no])
+  BUILD_TEST=""
 fi
 
 AC_MSG_CHECKING([whether to reduce exports])
@@ -873,9 +879,9 @@ AM_CONDITIONAL([TARGET_DARWIN], [test x$TARGET_OS = xdarwin])
 AM_CONDITIONAL([BUILD_DARWIN], [test x$BUILD_OS = xdarwin])
 AM_CONDITIONAL([TARGET_WINDOWS], [test x$TARGET_OS = xwindows])
 AM_CONDITIONAL([ENABLE_WALLET],[test x$enable_wallet = xyes])
-AM_CONDITIONAL([ENABLE_TESTS],[test x$use_tests = xyes])
+AM_CONDITIONAL([ENABLE_TESTS],[test x$BUILD_TEST = xyes])
 AM_CONDITIONAL([ENABLE_QT],[test x$bitcoin_enable_qt = xyes])
-AM_CONDITIONAL([ENABLE_QT_TESTS],[test x$use_tests$bitcoin_enable_qt_test = xyesyes])
+AM_CONDITIONAL([ENABLE_QT_TESTS],[test x$BUILD_TEST_QT = xyes])
 AM_CONDITIONAL([USE_QRCODE], [test x$use_qr = xyes])
 AM_CONDITIONAL([USE_LCOV],[test x$use_lcov = xyes])
 AM_CONDITIONAL([USE_COMPARISON_TOOL],[test x$use_comparison_tool != xno])
@@ -903,9 +909,6 @@ AC_SUBST(USE_QRCODE)
 AC_SUBST(BOOST_LIBS)
 AC_SUBST(TESTDEFS)
 AC_SUBST(LEVELDB_TARGET_FLAGS)
-AC_SUBST(BUILD_TEST)
-AC_SUBST(BUILD_QT)
-AC_SUBST(BUILD_TEST_QT)
 AC_SUBST(MINIUPNPC_CPPFLAGS)
 AC_SUBST(MINIUPNPC_LIBS)
 AC_SUBST(GMP_LIBS)