libticalcs: fix erroneous bashism in configure script

configure scripts are POSIX /bin/sh scripts and cannot have
bash-specific syntax. The `test xxx == yyy` construct with double equals
is a bash-specific alias for single equals. It does exactly the same
thing as single equals -- it provides no additional functionality, no
behavior changes, it is *exactly* the same but with an additional
alternate spelling. In exchange for doing nothing, it breaks muscle
memory when writing POSIX sh scripts and tricks developers into writing
the wrong thing.

It should never be used under any circumstances. Ideally it would be
removed altogether from GNU bash.

Bug: https://bugs.gentoo.org/723452

libticalcs/trunk/configure.ac

@@ -180,7 +180,7 @@ esac
 AC_ARG_VAR([CXX_FOR_BUILD], [C++ compiler for programs to be run on the build system])
 AC_ARG_VAR([CXXFLAGS_FOR_BUILD], [C++ compiler flags for CXX_FOR_BUILD])
 AC_MSG_CHECKING([for the host compiler])
-if test "x$build" == "x$host" ; then
+if test "x$build" = "x$host" ; then
   # Not cross-compiling.
   CXX_FOR_BUILD=$CXX
   CXXFLAGS_FOR_BUILD=$CXXFLAGS