Build our own sccache v0.8.1 package.

[nikolaszimmermann]

The system provided Ubuntu v0.7.7 package is broken:

📦 nzimmermann@wkdev:~/$ cat foo.cpp
int foo() {{
📦 nzimmermann@wkdev:~/$ /usr/bin/sccache g++ -o foo.o -c foo.cpp foo.cpp: In function 'int foo()':
foo.cpp:1:13: error: expected '}' at end of input
    1 | # 0 "foo.cpp"
      |            ~^
foo.cpp:1:13: error: expected '}' at end of input
    1 | # 0 "foo.cpp"
      |           ~ ^
foo.cpp:1:13: warning: no return statement in function returning non-void [-Wreturn-type]
sccache: Compiler killed by signal 1
📦 nzimmermann@wkdev:~/$ /usr/bin/sccache g++ -o foo.o -c foo.cpp
📦 nzimmermann@wkdev:~/$