Add `.clang-tidy` and `compile_flags.txt` to enable Clang-based tooling. (#208)

.clang-tidy

@@ -0,0 +1,27 @@
+# Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+# Exceptions. See /LICENSE for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+---
+Checks: '-*,readability-identifier-naming'
+WarningsAsErrors: true
+CheckOptions:
+  - { key: readability-identifier-naming.ClassCase, value: CamelCase }
+  - {
+      key: readability-identifier-naming.ConstexprVariableCase,
+      value: CamelCase,
+    }
+  - { key: readability-identifier-naming.FunctionCase, value: CamelCase }
+  - { key: readability-identifier-naming.ConstantCase, value: CamelCase }
+  - { key: readability-identifier-naming.NamespaceCase, value: CamelCase }
+  - { key: readability-identifier-naming.StructCase, value: CamelCase }
+  - {
+      key: readability-identifier-naming.TemplateParameterCase,
+      value: CamelCase,
+    }
+  - { key: readability-identifier-naming.TypeAliasCase, value: CamelCase }
+  - { key: readability-identifier-naming.TypedefCase, value: CamelCase }
+  - { key: readability-identifier-naming.UnionCase, value: CamelCase }
+  - { key: readability-identifier-naming.VariableCase, value: lower_case }
+  - { key: readability-identifier-naming.ParameterCase, value: lower_case }
+  - { key: readability-identifier-naming.ClassMemberCase, value: lower_case }

compile_flags.txt

@@ -0,0 +1,79 @@
+-xc++
+-Wall
+-Wextra
+-Wthread-safety
+-Wself-assign
+-Wno-missing-field-initializers
+-DLLVM_ON_UNIX=1
+-DHAVE_BACKTRACE=1
+-DBACKTRACE_HEADER=<execinfo.h>
+-DLTDL_SHLIB_EXT=".so"
+-DLLVM_ENABLE_THREADS=1
+-DHAVE_SYSEXITS_H=1
+-DHAVE_UNISTD_H=1
+-DHAVE_STRERROR_R=1
+-DHAVE_LIBPTHREAD=1
+-DHAVE_PTHREAD_GETNAME_NP=1
+-DHAVE_PTHREAD_SETNAME_NP=1
+-DHAVE_PTHREAD_GETSPECIFIC=1
+-D_GNU_SOURCE
+-DHAVE_LINK_H=1
+-DHAVE_LSEEK64=1
+-DHAVE_MALLINFO=1
+-DHAVE_POSIX_FALLOCATE=1
+-DHAVE_SBRK=1
+-DHAVE_STRUCT_STAT_ST_MTIM_TV_NSEC=1
+-DLLVM_NATIVE_ARCH="X86"
+-DLLVM_NATIVE_ASMPARSER=LLVMInitializeX86AsmParser
+-DLLVM_NATIVE_ASMPRINTER=LLVMInitializeX86AsmPrinter
+-DLLVM_NATIVE_DISASSEMBLER=LLVMInitializeX86Disassembler
+-DLLVM_NATIVE_TARGET=LLVMInitializeX86Target
+-DLLVM_NATIVE_TARGETINFO=LLVMInitializeX86TargetInfo
+-DLLVM_NATIVE_TARGETMC=LLVMInitializeX86TargetMC
+-DLLVM_HOST_TRIPLE="x86_64-unknown-linux-gnu"
+-DLLVM_DEFAULT_TARGET_TRIPLE="x86_64-unknown-linux-gnu"
+-DLLVM_ENABLE_TERMINFO=1
+-DLLVM_ENABLE_ZLIB=1
+-DGTEST_HAS_RTTI=0
+-D__STDC_LIMIT_MACROS
+-D__STDC_CONSTANT_MACROS
+-DGTEST_USE_OWN_TR1_TUPLE=1
+-iquote
+.
+-iquote
+bazel-bin
+-iquote
+bazel-carbon-lang/external/llvm-project
+-iquote
+bazel-bin/external/llvm-project
+-iquote
+bazel-carbon-lang/external/llvm_terminfo
+-iquote
+bazel-bin/external/llvm_terminfo
+-iquote
+bazel-carbon-lang/external/llvm_zlib
+-iquote
+bazel-bin/external/llvm_zlib
+-iquote
+bazel-carbon-lang/external/bazel_tools
+-iquote
+bazel-bin/external/bazel_tools
+-Ibazel-bin/external/llvm-project/llvm/_virtual_includes/gtest_internal_headers
+-isystem
+bazel-carbon-lang/external/llvm-project/llvm/include
+-isystem
+bazel-bin/external/llvm-project/llvm/include
+-isystem
+bazel-carbon-lang/external/llvm-project/llvm/utils/unittest/googlemock/include
+-isystem
+bazel-bin/external/llvm-project/llvm/utils/unittest/googlemock/include
+-isystem
+bazel-carbon-lang/external/llvm-project/llvm/utils/unittest/googletest/include
+-isystem
+bazel-bin/external/llvm-project/llvm/utils/unittest/googletest/include
+-std=c++17
+-no-canonical-prefixes
+-Wno-builtin-macro-redefined
+-D__DATE__="redacted"
+-D__TIMESTAMP__="redacted"
+-D__TIME__="redacted"