build: minor fixes to build on windows with make

This patch contains following fixes

1. Fix to build without PIC flag
2. Define LAPACK_COMPLEX_STRUCTURE for windows. Builds are failing
without it and changes are consistent with the CMake rules defined
in system.cmake (line 576)

Makefile.system

@@ -1536,7 +1536,7 @@ override FFLAGS     += $(COMMON_OPT) $(FCOMMON_OPT)
 override FPFLAGS    += $(FCOMMON_OPT) $(COMMON_PROF)
 #MAKEOVERRIDES =
 
-ifdef NEED_PIC
+ifeq ($(NEED_PIC), 1)
 ifeq (,$(findstring PIC,$(FFLAGS)))
 override FFLAGS += -fPIC
 endif
@@ -1566,6 +1566,7 @@ endif
 
 ifdef OS_WINDOWS
 LAPACK_CFLAGS +=  -DOPENBLAS_OS_WINDOWS
+LAPACK_CFLAGS +=  -DLAPACK_COMPLEX_STRUCTURE
 endif
 ifeq ($(C_COMPILER), LSB)
 LAPACK_CFLAGS +=  -DLAPACK_COMPLEX_STRUCTURE