Remove unnecessary conditional

This conditional is unnecessary as BUILD_PGM can be negated in the test.
Signed-off-by: Mikko Koppanen <mkoppanen@php.net>

configure.in

@@ -359,7 +359,6 @@ if test "x$gnu_compilers" = "xyes" -a "x$pgm_ext" = "xno"; then
 fi
 
 AM_CONDITIONAL(BUILD_PGM, test "x$pgm_ext" = "xyes")
-AM_CONDITIONAL(BUILD_NO_PGM, test "x$pgm_ext" = "xno")
 AM_CONDITIONAL(ON_MINGW, test "x$on_mingw32" = "xyes")
 
 AC_SUBST(stdint)

src/Makefile.am

@@ -243,7 +243,7 @@ libzmq_la_CXXFLAGS = -I$(top_srcdir)/foreign/openpgm/@pgm_basename@/openpgm/pgm/
     @LIBZMQ_EXTRA_CXXFLAGS@
 endif
 
-if BUILD_NO_PGM
+if !BUILD_PGM
 libzmq_la_CXXFLAGS = @LIBZMQ_EXTRA_CXXFLAGS@
 endif