Fixing build with as-needed

https://bugs.gentoo.org/show_bug.cgi?id=248552

--- a/configure.in
+++ b/configure.in
@@ -86,14 +86,9 @@
 AC_PATH_X
 AC_PATH_XTRA
 
-CFLAGS="$CFLAGS $X_CFLAGS"
-CXXFLAGS="$CXXFLAGS $X_CFLAGS"
-LDFLAGS="$LDFLAGS $X_LIBS $X_PRE_LIBS"
 dnl Checks for X libraries.
-AC_CHECK_LIB(X11, XOpenDisplay, LDFLAGS="$LDFLAGS -lX11",
-             AC_MSG_ERROR(XOpenDisplay not found in -lX11))
-
-LDFLAGS="$LDFLAGS $X_EXTRA_LIBS"
+AC_CHECK_LIB([X11], [XOpenDisplay], ,
+             AC_MSG_ERROR(XOpenDisplay not found in -lX11),)
 
 dnl Checks for header files.
 AC_HEADER_STDC
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,4 +1,4 @@
-CPPFLAGS =	@CPPFLAGS@ @INTERLACE@ @ISDN@\
+AM_CPPFLAGS =	 @INTERLACE@ @ISDN@\
 		-DGLOBAL_BB=\"$(datadir)/bbtools/bbppp.bb\" \
 		-DGLOBAL_NOBB=\"$(datadir)/bbtools/bbppp.nobb\"
 
@@ -16,4 +16,5 @@
 		 Basewindow.cc Basewindow.hh \
 		 blackboxstyle.hh
 EXTRA_DIST = BUGS TODO
-bbppp_LDADD = @X_LIBS@
+bbppp_LDADD  = @X_PRE_LIBS@ @X_LIBS@ @X_EXTRA_LIBS@
+bbppp_CFLAGS = @X_PRE_CFLAGS@ @X_CFLAGS@ @X_EXTRA_CFLAGS@