ccache: rework ccache management

 * ccache is now a normal package (both for the host and the target).

 * ccache option is now part of the "Build options" menu. It will
   automatically build ccache for the host before building anything,
   and will use it to cache builds for both host compilations and
   target compilations.

 * bump ccache to 3.1.3

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

1 files changed, 28 insertions, 3 deletions

diff --git a/docs/buildroot.html b/docs/buildroot.html
index f471962ad..b6cf578bd 100644
--- a/docs/buildroot.html
+++ b/docs/buildroot.html
@@ -29,6 +29,7 @@
       <li><a href="#buildroot_innards">How Buildroot works</a></li>
       <li><a href="#using_toolchain">Using the uClibc toolchain outside Buildroot</a></li>
       <li><a href="#external_toolchain">Use an external toolchain</a></li>
+      <li><a href="#ccache-support">Using <code>ccache</code> in Buildroot</li>
       <li><a href="#downloaded_packages">Location of downloaded packages</a></li>
       <li><a href="#add_packages">Adding new packages to Buildroot</a></li>
       <li><a href="#board_support">Creating your own board support</a></li>
@@ -523,9 +524,8 @@ $(ZLIB_DIR)/libz.a: $(ZLIB_DIR)/.configured
     <ul>
       <li><b>toolchain</b> (in the <code>toolchain/</code> directory) contains
       the Makefiles and associated files for all software related to the
-      cross-compilation toolchain: <code>binutils</code>, <code>ccache</code>,
-      <code>gcc</code>, <code>gdb</code>, <code>kernel-headers</code> and
-      <code>uClibc</code>.</li>
+      cross-compilation toolchain: <code>binutils</code>, <code>gcc</code>,
+      <code>gdb</code>, <code>kernel-headers</code> and <code>uClibc</code>.</li>
 
       <li><b>package</b> (in the <code>package/</code> directory) contains the
       Makefiles and associated files for all user-space tools that Buildroot
@@ -681,6 +681,31 @@ endif
     Build options -&gt; Toolchain and header file location</code> options.
     This could be useful if the toolchain must be shared with other users.</p>
 
+    <h2 id="ccache-support">Using <code>ccache</code> in Buildroot</h2>
+
+    <p><a href="http://ccache.samba.org">ccache</a> is a compiler
+    cache. It stores the object files resulting from each compilation
+    process, and is able to skip future compilation of the same source
+    file (with same compiler and same arguments) by using the
+    pre-existing object files. When doing almost identical builds from
+    scratch a number of times, it can nicely speed up the build
+    process.</p>
+
+    <p><code>ccache</code> support is integrated in Buildroot. You
+    just have to enable <code>Enable compiler cache</code>
+    in <code>Build options</code>. This will automatically build
+    <code>ccache</code> and use it for every host and target
+    compilation.</p>
+
+    <p>The cache is located
+    in <code>$HOME/.buildroot-ccache</code>. It is stored outside of
+    Buildroot output directory so that it can be shared by separate
+    Buildroot builds. If you want to get rid of the cache, simply
+    remove this directory.</p>
+
+    <p>You can get statistics on the cache (its size, number of hits,
+    misses, etc.) by running <code>make ccache-stats</code>.</p>
+
     <h2 id="downloaded_packages">Location of downloaded packages</h2>
 
     <p>It might be useful to know that the various tarballs that are