Ben Hutchings has announced that a backport of GCC 4.9 is now available for Debian GNU/Linux 7 LTS

Package : gcc-4.9-backport
Version : 4.9.2-10+deb7u1

GCC 4.9 has been packaged as gcc-4.9-backport for Debian 7. This
package will be needed by future updates to linux, and possibly other
packages, to implement the "retpoline" mitigation for CVE-2017-5715
(Spectre variant 2).

Further information about Debian LTS security advisories, how to apply
these updates to your system and frequently asked questions can be
found at: https://wiki.debian.org/LTS

  GCC-4.9-Backport New Package for Debian 7 LTS