[PATCH v3] Makefile: update 'make fuzz-all' docs to reflect modern clang

From: Andrzej Hunt <ajrhunt@google.com>

Clang no longer produces a libFuzzer.a. Instead, you can include libFuzzer by using -fsanitize=fuzzer. Therefore we should use that in the example command for building fuzzers.

We also add -fsanitize=fuzzer-no-link to the CFLAGS to ensure that all
the required instrumentation is added when compiling git [1], and remove
 -fsanitize-coverage=trace-pc-guard as it is deprecated.

I happen to have tested with LLVM 11 - however -fsanitize=fuzzer appears to work in a wide range of reasonably modern clangs.

(On my system: what used to be libFuzzer.a now lives under the following
 path, which is tricky albeit not impossible for a novice such as myself
 to find:
/usr/lib64/clang/11.0.0/lib/linux/libclang_rt.fuzzer-x86_64.a )

[1] https://releases.llvm.org/11.0.0/docs/LibFuzzer.html#fuzzer-usage

Signed-off-by: Andrzej Hunt <ajrhunt@google.com>
---
    Update 'make fuzz-all' docs to reflect modern clang
    
    This version of the patch fixes the commit message as per Junio's
    feedback. Thank you!

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-889%2Fahunt%2Ffuzz-docs-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-889/ahunt/fuzz-docs-v3
Pull-Request: https://github.com/gitgitgadget/git/pull/889

Range-diff vs v2:

 1:  f5b5a11966ca ! 1:  bc0d8b615410 Update 'make fuzz-all' docs to reflect modern clang
     @@ Metadata
      Author: Andrzej Hunt <ajrhunt@google.com>
      
       ## Commit message ##
     -    Update 'make fuzz-all' docs to reflect modern clang
     +    Makefile: update 'make fuzz-all' docs to reflect modern clang
      
     -    Clang no longer produces a libFuzzer.a, instead you can include
     -    libFuzzer by using -fsanitize=fuzzer. Therefore we should use
     -    that in the example command for building fuzzers.
     +    Clang no longer produces a libFuzzer.a. Instead, you can include
     +    libFuzzer by using -fsanitize=fuzzer. Therefore we should use that in
     +    the example command for building fuzzers.
      
     -    We also add -fsanitize=fuzzer-no-link to ensure that all the required
     -    instrumentation is added when compiling git [1], and remove
     +    We also add -fsanitize=fuzzer-no-link to the CFLAGS to ensure that all
     +    the required instrumentation is added when compiling git [1], and remove
           -fsanitize-coverage=trace-pc-guard as it is deprecated.
      
     -    I happen to have tested with LLVM 11 - however -fsanitize=fuzzer appears to
     -    work in a wide range of reasonably modern clangs.
     +    I happen to have tested with LLVM 11 - however -fsanitize=fuzzer appears
     +    to work in a wide range of reasonably modern clangs.
      
     -    (On my system: what used to be libFuzzer.a now lives under the following path,
     -     which is tricky albeit not impossible for a novice such as myself to find:
     +    (On my system: what used to be libFuzzer.a now lives under the following
     +     path, which is tricky albeit not impossible for a novice such as myself
     +     to find:
          /usr/lib64/clang/11.0.0/lib/linux/libclang_rt.fuzzer-x86_64.a )
      
          [1] https://releases.llvm.org/11.0.0/docs/LibFuzzer.html#fuzzer-usage

 Makefile | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)