configure: Fix --enable-XX-bit flags by moving LT_INIT where it should

Moving LT_INIT after setting completely (AM_)C(XX)FLAGS and LDFLAGS.
LT_INIT needs them as they are expected to be used all along
the compilation when the macro runs its tests to determine among other
things the host type.

For info, see http://www.gnu.org/software/libtool/manual/html_node/LT_005fINIT.html

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=50754
Signed-off-by: Alexandre Demers <alexandre.f.demers@gmail.com>
Tested-by: Tapani Palli <lemody@gmail.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>

configure.ac

@@ -57,9 +57,6 @@ AC_CHECK_PROGS([PYTHON2], [python2 python])
 AC_PROG_SED
 AC_PROG_MKDIR_P
 
-LT_PREREQ([2.2])
-LT_INIT([disable-static])
-
 AX_PROG_BISON([],
               AS_IF([test ! -f "$srcdir/src/glsl/glcpp/glcpp-parse.c"],
                     [AC_MSG_ERROR([bison not found - unable to compile glcpp-parse.y])]))
@@ -2190,6 +2187,14 @@ dnl Add user CFLAGS and CXXFLAGS
 CFLAGS="$CFLAGS $USER_CFLAGS"
 CXXFLAGS="$CXXFLAGS $USER_CXXFLAGS"
 
+dnl
+dnl LT_INIT adds tests to determine host based on some variables like (AM_)C(XX)FLAGS and (AM_)LDFLAGS.
+dnl They need to be set before calling LT_INIT so the macro can configure things correctly when cross_compiling.
+dnl This will allow --enable-xx-bit to work as expected.
+dnl
+LT_PREREQ([2.2])
+LT_INIT([disable-static])
+
 dnl Substitute the config
 AC_CONFIG_FILES([Makefile
 		src/Makefile