[llvm][lldb] use FindLibEdit.cmake everywhere

Currently, LLVM's LineEditor and LLDB both use libedit, but find them in different (inconsistent) ways.
This causes issues e.g. when you are using a locally installed version of libedit, which will not be used
by clang-query, but by lldb if picked up by FindLibEdit.cmake

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D124673

cmake/Modules/FindLibEdit.cmake

@@ -0,0 +1,70 @@
+#.rst:
+# FindLibEdit
+# -----------
+#
+# Find libedit library and headers
+#
+# The module defines the following variables:
+#
+# ::
+#
+#   LibEdit_FOUND          - true if libedit was found
+#   LibEdit_INCLUDE_DIRS   - include search path
+#   LibEdit_LIBRARIES      - libraries to link
+#   LibEdit_VERSION_STRING - version number
+
+if(LibEdit_INCLUDE_DIRS AND LibEdit_LIBRARIES)
+  set(LibEdit_FOUND TRUE)
+else()
+  find_package(PkgConfig QUIET)
+  pkg_check_modules(PC_LIBEDIT QUIET libedit)
+
+  find_path(LibEdit_INCLUDE_DIRS
+            NAMES
+              histedit.h
+            HINTS
+              ${PC_LIBEDIT_INCLUDEDIR}
+              ${PC_LIBEDIT_INCLUDE_DIRS}
+              "${CMAKE_INSTALL_FULL_INCLUDEDIR}")
+  find_library(LibEdit_LIBRARIES
+               NAMES
+                 edit libedit
+               HINTS
+                 ${PC_LIBEDIT_LIBDIR}
+                 ${PC_LIBEDIT_LIBRARY_DIRS}
+                 "${CMAKE_INSTALL_FULL_LIBDIR}")
+
+  if(LibEdit_INCLUDE_DIRS AND EXISTS "${LibEdit_INCLUDE_DIRS}/histedit.h")
+    file(STRINGS "${LibEdit_INCLUDE_DIRS}/histedit.h"
+         libedit_major_version_str
+         REGEX "^#define[ \t]+LIBEDIT_MAJOR[ \t]+[0-9]+")
+    string(REGEX REPLACE "^#define[ \t]+LIBEDIT_MAJOR[ \t]+([0-9]+)" "\\1"
+           LIBEDIT_MAJOR_VERSION "${libedit_major_version_str}")
+
+    file(STRINGS "${LibEdit_INCLUDE_DIRS}/histedit.h"
+         libedit_minor_version_str
+         REGEX "^#define[ \t]+LIBEDIT_MINOR[ \t]+[0-9]+")
+    string(REGEX REPLACE "^#define[ \t]+LIBEDIT_MINOR[ \t]+([0-9]+)" "\\1"
+           LIBEDIT_MINOR_VERSION "${libedit_minor_version_str}")
+
+    set(LibEdit_VERSION_STRING "${libedit_major_version}.${libedit_minor_version}")
+  endif()
+
+  include(FindPackageHandleStandardArgs)
+  find_package_handle_standard_args(LibEdit
+                                    FOUND_VAR
+                                      LibEdit_FOUND
+                                    REQUIRED_VARS
+                                      LibEdit_INCLUDE_DIRS
+                                      LibEdit_LIBRARIES
+                                    VERSION_VAR
+                                      LibEdit_VERSION_STRING)
+  mark_as_advanced(LibEdit_INCLUDE_DIRS LibEdit_LIBRARIES)
+endif()
+
+if (LibEdit_FOUND AND NOT TARGET LibEdit::LibEdit)
+  add_library(LibEdit::LibEdit UNKNOWN IMPORTED)
+  set_target_properties(LibEdit::LibEdit PROPERTIES
+                        IMPORTED_LOCATION ${LibEdit_LIBRARIES}
+                        INTERFACE_INCLUDE_DIRECTORIES ${LibEdit_INCLUDE_DIRS})
+endif()