docs: Add a new page with common cross/native file options [skip ci]

Rather than having two separate sections with duplicated information
lets just have one for the common settings, and only document sections
specific to each file in separately

1 files changed, 3 insertions, 51 deletions

diff --git a/docs/markdown/Native-environments.md b/docs/markdown/Native-environments.md
index a046ee9..8dcce2a 100644
--- a/docs/markdown/Native-environments.md
+++ b/docs/markdown/Native-environments.md
@@ -19,69 +19,21 @@ persistent environment:
 * To build with a non-default native tool chain (such as clang instead of gcc)
 * To use a non-default version of another binary, such as yacc, or llvm-config
 
-
 ## Changing native file settings
 
 All of the rules about cross files and changed settings apply to native files
 as well, see [here](Cross-compilation.md#changing-cross-file-settings)
 
-
 ## Defining the environment
 
-### Binaries
-
-Currently the only use of native files is to override native binaries. This
-includes the compilers and binaries collected with `find_program`, and those
-used by dependencies that use a config-tool instead of pkgconfig for detection,
-like `llvm-config`
-
-```ini
-[binaries]
-c = '/usr/local/bin/clang'
-cpp = '/usr/local/bin/clang++'
-rust = '/usr/local/bin/rust'
-c_ld = 'gold'
-cpp_ld = 'gold'
-rust_ld = 'gold'
-llvm-config = '/usr/local/llvm-svn/bin/llvm-config'
-```
-
-### Paths and Directories
-
-As of 0.50.0 paths and directories such as libdir can be defined in the native
-file in a paths section
-
-```ini
-[paths]
-libdir = 'mylibdir'
-prefix = '/my prefix'
-```
-
-These values will only be loaded when not cross compiling. Any arguments on the
-command line will override any options in the native file. For example, passing
-`--libdir=otherlibdir` would result in a prefix of `/my prefix` and a libdir of
-`otherlibdir`.
-
-
-## Loading multiple native files
-
-Native files allow layering (cross files can be layered since meson 0.52.0).
-More than one native file can be loaded, with values from a previous file being
-overridden by the next. The intention of this is not overriding, but to allow
-composing native files.
-
-For example, if there is a project using C and C++, python 3.4-3.7, and LLVM
-5-7, and it needs to build with clang 5, 6, and 7, and gcc 5.x, 6.x, and 7.x;
-expressing all of these configurations in monolithic configurations would
-result in 81 different native files. By layering them, it can be expressed by
-just 12 native files.
-
+See the [config-files section](Machine-files.md), for options shared by cross
+and native files.
 
 ## Native file locations
 
 Like cross files, native files may be installed to user or system wide
 locations, defined as:
-  - $XDG_DATA_DIRS/meson/native 
+  - $XDG_DATA_DIRS/meson/native
     (/usr/local/share/meson/native:/usr/share/meson/native if $XDG_DATA_DIRS is
     undefined)
   - $XDG_DATA_HOME/meson/native ($HOME/.local/share/meson/native if