configure.ac: add -fpic flag

relocation R_X86_64_32 against `.bss' can not be used when making a
shared object.

Change-Id: I9ca43820c9644f4b238ac44f8eaac29c4b2fd52c
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/configure.ac b/configure.ac
index fc9cd8e..55c8a43 100644
--- a/configure.ac
+++ b/configure.ac
@@ -18,7 +18,7 @@
 
 # Checks for typedefs, structures, and compiler characteristics.
 AX_CXX_COMPILE_STDCXX_14([noext])
-AX_APPEND_COMPILE_FLAGS([-Wall -Werror], [CXXFLAGS])
+AX_APPEND_COMPILE_FLAGS([-fpic -Wall -Werror], [CXXFLAGS])
 
 # Checks for libraries.
 # AC_CHECK_LIB([mapper], [mapper_get_service], ,[AC_MSG_ERROR([Could not find libmapper...openbmc/phosphor-objmgr package required])])