[Docs] Mention that compier-rt's check-all depend on clang

[xgupta]

Summary

When we don't add clang to -DLLVM_ENABLE_PROJECTS an cmake error shows:

CMake Error at cmake/modules/AddLLVM.cmake:1814 (add_dependencies):

The dependency target "clang" of target "check-all" does not exist.

Call Stack (most recent call first):

CMakeLists.txt:1071 (add_lit_target)

CMake Error at cmake/modules/AddLLVM.cmake:1814 (add_dependencies):

The dependency target "clang-resource-headers" of target "check-all" does
not exist.

Call Stack (most recent call first):

CMakeLists.txt:1071 (add_lit_target)

Although build was succussful but when run chack-all an error occurs:

make[3]: *** No rule to make target 'projects/compiler-rt/lib/sanitizer_common/tests/clang', needed by 'projects/compiler-rt/lib/sanitizer_common/tests/Sanitizer-x86_64-Test-Nolibc'. Stop.

[xgupta]

ping @dvyukov, Does this patch need a review or It was my mistake in configure step.

[MaskRay]

The page looks outdated. It may need to be converted to .rst.
The cmake ../compiler-rt configuration seems like a not-recommended way for Clang. Maybe it is still used by GCC sanitizers.

For Clang, if -DLLVM_ENABLE_PROJECTS= -DLLVM_ENABLE_RUNTIMES=compiler-rt is used (clang not listed), it will fail early in CMake.

[xgupta]

In D113009#3149832, @MaskRay wrote:

The page looks outdated. It may need to be converted to .rst.

Ok, Thanks for taking a look. I will send a patch for that on sunday. I think a few pages of clang are also written in .html in clang/www/ directory so they also need an update, will send a patch soon.

The cmake ../compiler-rt configuration seems like a not-recommended way for Clang. Maybe it is still used by GCC sanitizers.

For Clang, if -DLLVM_ENABLE_PROJECTS= -DLLVM_ENABLE_RUNTIMES=compiler-rt is used (clang not listed), it will fail early in CMake.

I will read the compiler-rt/CMakeLists.txt and rewrite what changes are needed in .rst file.

[xgupta]

Will do it later.

compiler-rt/www/index.html

<div id="content">
   <li>mkdir build-compiler-rt</li>
   <li>cd build-compiler-rt</li>
   <li>cmake ../compiler-rt -DLLVM_CONFIG_PATH=/path/to/llvm-config</li>
   <li>make</li>
   </ul>
 
   <p>Tests for sanitizer runtimes are ported to
   <a href="https://llvm.org/docs/CommandGuide/lit.html">llvm-lit</a> and are
-  run by <b>make check-all</b> command in LLVM/Clang/compiler-rt build tree.</p>
+  run by <b>make check-all</b> command in LLVM/Clang/compiler-rt build tree.
+  Note that to run the check-all target, clang also need to enabled with
+  -DLLVM_ENABLE_PROJECTS option.</p>
 
   <p>compiler-rt libraries are installed to the system with <b>make install</b>
   command in either LLVM/Clang/compiler-rt or standalone
   compiler-rt build tree.</p>
 
   <p>compiler-rt doesn't have its own mailing list, if you have questions please
      email the <a
     href="https://lists.llvm.org/mailman/listinfo/llvm-dev">llvm-dev</a> mailing
     list.  Commits to the compiler-rt SVN module are automatically sent to the
     <a
   href="https://lists.llvm.org/mailman/listinfo/llvm-commits">llvm-commits</a>
     mailing list.</p>
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