Boinc: Avoiding unexpected dependencies

In reaction to a comment by @hnyman in
https://github.com/openwrt/packages/pull/11768#issuecomment-610513948
on BOINC embracing too many libraries it finds on its build
host, the inclusion of the freetype library is now excluded
by an embracing "if" statement.

The patch is presented to BOINC upstream at
https://github.com/BOINC/boinc/pull/3578

Signed-off-by: Steffen Möller <moeller@debian.org>

net/boinc/patches/001-avoidExtraDependencies

@@ -0,0 +1,15 @@
+Index: boinc-client_release-7.16-7.16.5/configure.ac
+===================================================================
+--- boinc-client_release-7.16-7.16.5.orig/configure.ac
++++ boinc-client_release-7.16-7.16.5/configure.ac
+@@ -506,8 +506,10 @@ SAH_CHECK_LIB([dl], [dlopen],
+     [BOINC_EXTRA_LIBS="${BOINC_EXTRA_LIBS} ${sah_lib_last}"])
+ SAH_CHECK_LIB([nsl], [gethostbyname],
+     [BOINC_EXTRA_LIBS="${BOINC_EXTRA_LIBS} ${sah_lib_last}"])
++if test "${enable_manager}" = yes ; then
+ SAH_CHECK_LIB([freetype], [fopen],
+     [BOINC_EXTRA_LIBS="${BOINC_EXTRA_LIBS} ${sah_lib_last}"])
++fi
+ SAH_CHECK_LIB([socket], [bind],
+     [BOINC_EXTRA_LIBS="${BOINC_EXTRA_LIBS} ${sah_lib_last}"])
+ SAH_CHECK_LIB([z], [gzopen],