[clang-tools-extra][cmake] Use GNUInstallDirs to support custom ins…

…tallation dirs.

This is the original patch in my GNUInstallDirs series, now last to merge as the final piece!

It arose as a new draft of D28234. I initially did the unorthodox thing of pushing to that when I wasn't the original author, but since I ended up

 - Using `GNUInstallDirs`, rather than mimicking it, as the original author was hesitant to do but others requested.

 - Converting all the packages, not just LLVM, effecting many more projects than LLVM itself.

I figured it was time to make a new revision.

I have used this patch series (and many back-ports) as the basis of NixOS/nixpkgs#111487 for my distro (NixOS), which was merged last spring (2021). It looked like people were generally on board in D28234, but I make note of this here in case extra motivation is useful.

---

As pointed out in the original issue, a central tension is that LLVM already has some partial support for these sorts of things. Variables like `COMPILER_RT_INSTALL_PATH` have already been dealt with. Variables like `LLVM_LIBDIR_SUFFIX` however, will require further work, so that we may use `CMAKE_INSTALL_LIBDIR`.

These remaining items will be addressed in further patches. What is here is now rote and so we should get it out of the way before dealing more intricately with the remainder.

Reviewed By: #libunwind, #libc, #libc_abi, compnerd

Differential Revision: https://reviews.llvm.org/D99484

clang-tools-extra/CMakeLists.txt

@@ -1,4 +1,5 @@
 include(CMakeDependentOption)
+include(GNUInstallDirs)
 
 option(CLANG_TIDY_ENABLE_STATIC_ANALYZER
   "Include static analyzer checks in clang-tidy" ON)

clang-tools-extra/clang-doc/tool/CMakeLists.txt

@@ -19,9 +19,9 @@ target_link_libraries(clang-doc
   )
 
 install(FILES ../assets/clang-doc-default-stylesheet.css
-  DESTINATION share/clang
+  DESTINATION "${CMAKE_INSTALL_DATADIR}/clang"
   COMPONENT clang-doc)
 
 install(FILES ../assets/index.js
-  DESTINATION share/clang
+  DESTINATION "${CMAKE_INSTALL_DATADIR}/clang"
   COMPONENT clang-doc)

clang-tools-extra/clang-include-fixer/find-all-symbols/tool/CMakeLists.txt

@@ -20,5 +20,5 @@ target_link_libraries(find-all-symbols
   )
 
 install(PROGRAMS run-find-all-symbols.py
-  DESTINATION share/clang
+  DESTINATION "${CMAKE_INSTALL_DATADIR}/clang"
   COMPONENT find-all-symbols)

clang-tools-extra/clang-include-fixer/tool/CMakeLists.txt

@@ -21,8 +21,8 @@ target_link_libraries(clang-include-fixer
   )
 
 install(PROGRAMS clang-include-fixer.el
-  DESTINATION share/clang
+  DESTINATION "${CMAKE_INSTALL_DATADIR}/clang"
   COMPONENT clang-include-fixer)
 install(PROGRAMS clang-include-fixer.py
-  DESTINATION share/clang
+  DESTINATION "${CMAKE_INSTALL_DATADIR}/clang"
   COMPONENT clang-include-fixer)

clang-tools-extra/clang-tidy/CMakeLists.txt

@@ -113,7 +113,7 @@ add_subdirectory(utils)
 
 if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
   install(DIRECTORY .
-    DESTINATION include/clang-tidy
+    DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/clang-tidy"
     COMPONENT clang-tidy-headers
     FILES_MATCHING
     PATTERN "*.h"

clang-tools-extra/clang-tidy/tool/CMakeLists.txt

@@ -52,9 +52,9 @@ target_link_libraries(clang-tidy
 
 
 install(PROGRAMS clang-tidy-diff.py
-  DESTINATION share/clang
+  DESTINATION "${CMAKE_INSTALL_DATADIR}/clang"
   COMPONENT clang-tidy)
 install(PROGRAMS run-clang-tidy.py
-  DESTINATION bin
+  DESTINATION "${CMAKE_INSTALL_BINDIR}"
   COMPONENT clang-tidy
   RENAME run-clang-tidy)

clang-tools-extra/modularize/CMakeLists.txt

@@ -23,5 +23,5 @@ clang_target_link_libraries(modularize
   )
 
 install(TARGETS modularize
-        RUNTIME DESTINATION bin
+        RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}"
         COMPONENT clang-extras)