/usr/src/gcc-8/debian/patches/gcc-linaro.diff is in gcc-8-source 8-20180414-1ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 | # DP: Changes for the Linaro 8-2018.xx snapshot.
MSG=$(git log origin/linaro/gcc-8-branch --format=format:"%s" -n 1 --grep "Merge branches"); SVN=${MSG##* }; git log origin/gcc-7-branch --format=format:"%H" -n 1 --grep "gcc-7-branch@${SVN%.}"
LANG=C git diff --no-renames bb85d61e6bfbadee4494e034a5d8187cf0626aed 1604249e382610b087a72d0d07103f815458cec0 \
| egrep -v '^(diff|index) ' \
| filterdiff --strip=1 --addoldprefix=a/src/ --addnewprefix=b/src/ \
| sed 's,a/src//dev/null,/dev/null,'
|