Here's the last lines of text before the error showed up:

Perl.c:1356:5: note: in expansion of macro 'dVAR'
dVAR; dXSARGS;

Perl.c: In function 'XS_DBD__Perl__st_FETCH_attrib':
C:\Dwimperl\perl\lib\CORE/perl.h:340:39: warning: unused variable 'Perl___notused' -Wunused-variable #define dNOOP extern int /*@unused@*/ Perl___notused PERL_UNUSED_DECL

C:\Dwimperl\perl\lib\CORE/perl.h:162:17: note: in expansion of macro 'dNOOP'
# define dVAR dNOOP

Perl.c:1384:5: note: in expansion of macro 'dVAR'
dVAR; dXSARGS;

Perl.c: In function 'XS_DBD__Perl__st_DESTROY':
C:\Dwimperl\perl\lib\CORE/perl.h:340:39: warning: unused variable 'Perl___notused' -Wunused-variable
#define dNOOP extern int /*@unused@*/ Perl___notused PERL_UNUSED_DECL

^ C:\Dwimperl\perl\lib\CORE/perl.h:162:17: note: in expansion of macro 'dNOOP'
# define dVAR dNOOP

Perl.c:1412:5: note: in expansion of macro 'dVAR'
dVAR; dXSARGS;

Perl.c: In function 'boot_DBD__Perl':
C:\Dwimperl\perl\lib\CORE/perl.h:340:39: warning: unused variable 'Perl___notused' -Wunused-variable
#define dNOOP extern int /*@unused@*/ Perl___notused PERL_UNUSED_DECL

C:\Dwimperl\perl\lib\CORE/perl.h:162:17: note: in expansion of macro 'dNOOP'
# define dVAR dNOOP

Perl.c:1470:5: note: in expansion of macro 'dVAR'
dVAR; dXSARGS;

Aren't these warnings because of  -Wunused-variable? Is there a line where it says "error:" ? I am afraid to ask you to post the full log in case it's too big.