How do I compile gcc-5 from source?

It looks like gcc-5 was recently removed from Debian's unstable repository. I need gcc-5 to compile an older Linux kernel (3.19) and so I am looking to build it from source, through this is causing me a great deal of trouble. I have been following the instructions found here , but I find myself wondering what settings I need to set and more. Thus far, I have done the following. 1. Downloaded and unpacked the source code. 2. Configured gcc-5 by doing the following:

% mkdir objdir
% cd objdir
% ../gcc-5.4.0/configure (I included neither options nor target flags)

3. Attempted to build using the following in my objdir directory:

% make BOOT_CFLAGS='-O' bootstrap

However, bootstrapping raised errors that prevented me from moving onto the install. After running for about 5 minutes, I encounter the following errors:

In file included from ../../../../gcc-5.4.0/libgcc/unwind-dw2.c:401:0:
./md-unwind-support.h: In function 'x86_fallback_frame_state':
./md-unwind-support.h:141:18: error: field 'uc' has incomplete type
struct ucontext uc;
                ^
make: *** [../../../../gcc-5.4.0/libgcc/shared-object.mk:14: unwind-dw2.o] Error 1
make: Leaving directory '/home/me/objdir/x86_64-unknown-linux-gnu/32/libgcc'
make: *** [Makefile:1154: multi-do] Error 1
make: Leaving directory '/home/me/objdir/x86_64-unknown-linux-gnu/libgcc'
make: *** [Makefile:119: multi-do] Error 2
make: Leaving directory '/home/me/objdir/x86_64-unknown-linux-gnu/libgcc'
make[2] : *** [Makefile:16510: all-stage1-target-libgcc] Error 2
make[2] : Leaving directory '/home/me/objdir'
make[1] : *** [Makefile:22461: stage1-bubble] Error 2
make[1] : Leaving directory '/home/me/objdir'
make: *** [Makefile:22798: bootstrap] Error 2

I am running Debian 10 (Buster) and have the necessary prerequisites installed as listed here . Any help or guidance either in fixing the errors I have during bootstrapping or with building from source in general would be much appreciated! Thank you.