Add extra parameter to pass vendor LDFLAGS for libsai.so (#1291)

Since vendor libsai.so may require some extra libs we need
to pass this as a param for linker

configure.ac

@@ -207,12 +207,17 @@ CXXFLAGS="$SAVED_FLAGS"
 
 AC_SUBST(CXXFLAGS_COMMON)
 
+AC_ARG_WITH(extra-libsai-ldflags,
+[  --with-extra-libsai-ldflags=FLAGS
+                          extra libsai.so flags for vendor library],
+[AC_SUBST(EXTRA_LIBSAI_LDFLAGS, "${withval}")])
+
 AC_SUBST(SAIINC, "-I\$(top_srcdir)/SAI/inc -I\$(top_srcdir)/SAI/experimental -I\$(top_srcdir)/SAI/meta")
 
 AM_COND_IF([SYNCD], [
 AM_COND_IF([SAIVS], [], [
 SAVED_FLAGS="$CXXFLAGS"
-CXXFLAGS="-Xlinker --no-as-needed -lsai -I$srcdir/SAI/inc -I$srcdir/SAI/experimental -I$srcdir/SAI/meta"
+CXXFLAGS="-Xlinker --no-as-needed -lsai -I$srcdir/SAI/inc -I$srcdir/SAI/experimental -I$srcdir/SAI/meta $EXTRA_LIBSAI_LDFLAGS"
 AC_CHECK_FUNCS(sai_query_api_version, [
 AC_MSG_CHECKING([SAI headers API version and library version check])
 AC_TRY_RUN([

saidiscovery/Makefile.am

@@ -13,4 +13,4 @@ saidiscovery_SOURCES = saidiscovery.cpp
 saidiscovery_CPPFLAGS = $(CODE_COVERAGE_CPPFLAGS)
 saidiscovery_CXXFLAGS = $(DBGFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS_COMMON) $(CODE_COVERAGE_CXXFLAGS)
 saidiscovery_LDADD = -lhiredis -lswsscommon $(top_srcdir)/syncd/libSyncd.a $(SAILIB) -lpthread \
-					 -L$(top_srcdir)/meta/.libs -lsaimetadata -lsaimeta -lzmq $(CODE_COVERAGE_LIBS)
+					 -L$(top_srcdir)/meta/.libs -lsaimetadata -lsaimeta -lzmq $(CODE_COVERAGE_LIBS) $(EXTRA_LIBSAI_LDFLAGS)

saisdkdump/Makefile.am

@@ -11,4 +11,4 @@ endif
 saisdkdump_SOURCES = saisdkdump.cpp
 saisdkdump_CPPFLAGS = $(CODE_COVERAGE_CPPFLAGS)
 saisdkdump_CXXFLAGS = $(DBGFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS_COMMON) $(CODE_COVERAGE_CXXFLAGS)
-saisdkdump_LDADD = -lhiredis -lswsscommon $(SAILIB) -lpthread -L$(top_srcdir)/meta/.libs -lsaimetadata -lsaimeta -lzmq $(CODE_COVERAGE_LIBS)
+saisdkdump_LDADD = -lhiredis -lswsscommon $(SAILIB) -lpthread -L$(top_srcdir)/meta/.libs -lsaimetadata -lsaimeta -lzmq $(CODE_COVERAGE_LIBS) $(EXTRA_LIBSAI_LDFLAGS)

syncd/Makefile.am

@@ -68,7 +68,7 @@ endif
 syncd_CPPFLAGS = $(CODE_COVERAGE_CPPFLAGS)
 syncd_CXXFLAGS = $(DBGFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS_COMMON) $(CODE_COVERAGE_CXXFLAGS) $(CFLAGS_ASAN)
 syncd_LDADD = libSyncd.a $(top_srcdir)/lib/libSaiRedis.a -L$(top_srcdir)/meta/.libs -lsaimetadata -lsaimeta \
-			  -ldl -lhiredis -lswsscommon $(SAILIB) -lpthread -lzmq $(CODE_COVERAGE_LIBS)
+			  -ldl -lhiredis -lswsscommon $(SAILIB) -lpthread -lzmq $(CODE_COVERAGE_LIBS) $(EXTRA_LIBSAI_LDFLAGS)
 syncd_LDFLAGS = $(LDFLAGS_ASAN) -rdynamic
 
 if SAITHRIFT