Gcc complains sigcontext structures in files 
/usr/include/bits/sigcontext.h and
/usr/include/asm-sparc/sigcontext.h, 
although the structure is defined identically in both files. 
Hence, I just added:

#ifndef <macro-name>
#define <macro-name>

around sigcontext structure in /usr/include/bits/sigcontext.h. And in
/usr/include/asm-sparc/sigcontext.h, I added #ifndef <macro-name>, 
to make sure that only struct from one of the 2 file's is getting included.