Add a reduced copy of the llvm .gitignore

as a start for the monorepo .gitignore.

llvm-svn: 357961

.gitignore

@@ -0,0 +1,56 @@
+#==============================================================================#
+# This file specifies intentionally untracked files that git should ignore.
+# See: http://www.kernel.org/pub/software/scm/git/docs/gitignore.html
+#
+# This file is intentionally different from the output of `git svn show-ignore`,
+# as most of those are useless.
+#==============================================================================#
+
+#==============================================================================#
+# File extensions to be ignored anywhere in the tree.
+#==============================================================================#
+# Temp files created by most text editors.
+*~
+# Merge files created by git.
+*.orig
+# Byte compiled python modules.
+*.pyc
+# vim swap files
+.*.sw?
+.sw?
+#OS X specific files.
+.DS_store
+
+# Nested build directory
+/build
+
+#==============================================================================#
+# Explicit files to ignore (only matches one).
+#==============================================================================#
+# Various tag programs
+/tags
+/TAGS
+/GPATH
+/GRTAGS
+/GSYMS
+/GTAGS
+.gitusers
+autom4te.cache
+cscope.files
+cscope.out
+autoconf/aclocal.m4
+autoconf/autom4te.cache
+/compile_commands.json
+# Visual Studio built-in CMake configuration
+/CMakeSettings.json
+# CLion project configuration
+/.idea
+
+#==============================================================================#
+# Directories to ignore (do not add trailing '/'s, they skip symlinks).
+#==============================================================================#
+# VS2017 and VSCode config files.
+.vscode
+.vs
+# clangd index
+.clangd