The gdb-7.7.1-15.fc21 build fails with the following errors. -15 built fine and it looks like the main change was to drop build with gcc-java so I'm not sure if there's another distro change coming into play here.

http://arm.koji.fedoraproject.org/koji/taskinfo?taskID=2357682

gcc -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches      -I. -I../../gdb -I../../gdb/common -I../../gdb/config -DLOCALEDIR="\"/usr/share/locale\"" -DHAVE_CONFIG_H -I../../gdb/../include/opcode -I../../gdb/../opcodes/..  -I../bfd -I../../gdb/../bfd -I../../gdb/../include -I../libdecnumber -I../../gdb/../libdecnumber  -I../../gdb/gnulib/import -Ibuild-gnulib/import   -DTUI=1  -I/usr/include/python2.7 -I/usr/include/python2.7 -Wall -Wdeclaration-after-statement -Wpointer-arith -Wpointer-sign -Wno-unused -Wunused-value -Wunused-function -Wno-switch -Wno-char-subscripts -Wmissing-prototypes -Wdeclaration-after-statement -Wempty-body -Wmissing-parameter-type -Wold-style-declaration -Wold-style-definition -Wformat-nonliteral -Wno-unused  -c -o proc-service.o -MT proc-service.o -MMD -MP -MF .deps/proc-service.Tpo ../../gdb/proc-service.c
../../gdb/aarch64-linux-nat.c: In function 'aarch64_linux_set_debug_regs':
../../gdb/aarch64-linux-nat.c:311:29: error: storage size of 'regs' isn't known
   struct user_hwdebug_state regs;
                             ^
In file included from /usr/include/signal.h:342:0,
                 from ../../gdb/linux-nat.h:22,
                 from ../../gdb/aarch64-linux-nat.c:26:
../../gdb/aarch64-linux-nat.c:322:35: error: invalid use of undefined type 'struct user_hwdebug_state'
   iov.iov_len = (offsetof (struct user_hwdebug_state, dbg_regs[count - 1])
                                   ^
../../gdb/aarch64-linux-nat.c: In function 'aarch64_linux_get_debug_reg_capacity':
../../gdb/aarch64-linux-nat.c:784:29: error: storage size of 'dreg_state' isn't known
   struct user_hwdebug_state dreg_state;
                             ^
../../gdb/aarch64-linux-nat.c: In function '_initialize_aarch64_linux_nat':
../../gdb/aarch64-linux-nat.c:1539:37: warning: assignment from incompatible pointer type
   t->to_region_ok_for_hw_watchpoint =
                                     ^
../../gdb/aarch64-linux-nat.c:1541:27: warning: assignment from incompatible pointer type
   t->to_insert_watchpoint = aarch64_linux_insert_watchpoint;
                           ^
../../gdb/aarch64-linux-nat.c:1542:27: warning: assignment from incompatible pointer type
   t->to_remove_watchpoint = aarch64_linux_remove_watchpoint;
                           ^
../../gdb/aarch64-linux-nat.c:1545:38: warning: assignment from incompatible pointer type
   t->to_watchpoint_addr_within_range =
                                      ^
gcc -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches      -I. -I../../gdb -I../../gdb/common -I../../gdb/config -DLOCALEDIR="\"/usr/share/locale\"" -DHAVE_CONFIG_H -I../../gdb/../include/opcode -I../../gdb/../opcodes/..  -I../bfd -I../../gdb/../bfd -I../../gdb/../include -I../libdecnumber -I../../gdb/../libdecnumber  -I../../gdb/gnulib/import -Ibuild-gnulib/import   -DTUI=1  -I/usr/include/python2.7 -I/usr/include/python2.7 -Wall -Wdeclaration-after-statement -Wpointer-arith -Wpointer-sign -Wno-unused -Wunused-value -Wunused-function -Wno-switch -Wno-char-subscripts -Wmissing-prototypes -Wdeclaration-after-statement -Wempty-body -Wmissing-parameter-type -Wold-style-declaration -Wold-style-definition -Wformat-nonliteral -Wno-unused  -c -o linux-thread-db.o -MT linux-thread-db.o -MMD -MP -MF .deps/linux-thread-db.Tpo ../../gdb/linux-thread-db.c
make[2]: *** [aarch64-linux-nat.o] Error 1
make[2]: *** Waiting for unfinished jobs....
make[2]: Leaving directory `/builddir/build/BUILD/gdb-7.7.1/build-aarch64-redhat-linux-gnu/gdb'
make[1]: *** [all-gdb] Error 2
make[1]: Leaving directory `/builddir/build/BUILD/gdb-7.7.1/build-aarch64-redhat-linux-gnu'
make: *** [all] Error 2