Make README a proper Markdown file

It was already using Markdown-alike syntax. Let's just go the full length,
and make it a proper Markdown file.

Change-Id: I6b0dcbc9118e9b31aebef30db85a244a100f6eff
Reviewed-by: Cristian Adam <cristian.adam@qt.io>
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

1 files changed, 131 insertions, 0 deletions

diff --git a/README.md b/README.md
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+HOW TO BUILD Qt6
+================
+
+
+Synopsis
+========
+
+System requirements
+------------------
+
+* CMake 3.18 or later
+* Perl 5.8 or later
+* Python 2.7 or later
+* C++ compiler supporting the C++17 standard
+
+It's recommended to have ninja 1.8 or later installed.
+
+For other platform specific requirements,
+please see section "Setting up your machine" on:
+http://wiki.qt.io/Get_The_Source
+
+Linux, Mac:
+-----------
+
+````
+cd <path>/<source_package>
+./configure -prefix $PWD/qtbase
+cmake --build .
+````
+
+Windows:
+--------
+
+1. Open a command prompt.
+2. Ensure that the following tools can be found in the path:
+ * Supported compiler (Visual Studio 2019 or later, or MinGW-builds gcc 8.1 or later)
+ * Perl version 5.12 or later   [http://www.activestate.com/activeperl/]
+ * Python version 2.7 or later  [http://www.activestate.com/activepython/]
+ * Ruby version 1.9.3 or later  [http://rubyinstaller.org/]
+
+````
+cd <path>\<source_package>
+configure -prefix %CD%\qtbase
+cmake --build .
+````
+
+More details follow.
+
+Build!
+======
+
+Qt is built with CMake, and a typical
+`configure && cmake --build .` build process is used.
+
+If ninja is installed, it is automatically chosen as CMake generator.
+
+Some relevant configure options (see configure -help):
+
+* `-release` Compile and link Qt with debugging turned off.
+* `-debug` Compile and link Qt with debugging turned on.
+
+Example for a release build:
+
+````
+./configure -prefix $PWD/qtbase
+cmake --build .
+````
+
+Example for a developer build:
+(enables more autotests, builds debug version of libraries, ...)
+
+````
+./configure -developer-build
+cmake --build .
+````
+
+ See output of `./configure -help` for documentation on various options to
+ configure.
+
+ The above examples will build whatever Qt modules have been enabled
+ by default in the build system.
+
+ It is possible to build selected repositories with their dependencies by doing
+ a `ninja <repo-name>/all'.  For example, to build only qtdeclarative,
+ and the modules it depends on:
+
+````
+./configure
+ninja qtdeclarative/all
+````
+
+This can save a lot of time if you are only interested in a subset of Qt.
+
+
+Hints
+=====
+
+The submodule repository `qtrepotools` contains useful scripts for
+developers and release engineers. Consider adding qtrepotools/bin
+to your `PATH` environment variable to access them.
+
+
+Building Qt from git
+=====================
+See http://wiki.qt.io/Building_Qt_6_from_Git and README.git
+for more information.
+See http://wiki.qt.io/Qt_6 for the reference platforms.
+
+
+Documentation
+=============
+
+After configuring and compiling Qt, building the documentation is possible by running
+
+```
+cmake --build . --target docs
+```
+
+After having built the documentation, you need to install it with the following
+command:
+
+```
+cmake --build . --target install_docs
+```
+
+The documentation is installed in the path specified with the
+configure argument `-docdir`.
+
+Information about Qt's documentation is located in qtbase/doc/README
+
+Note: Building the documentation is only tested on desktop platforms.