aDd support for building a subset of the llvm tools, patch by Jeffrey Yasskin!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@70082 91177308-0d34-0410-b5e6-96231b3b80d8

docs/GettingStarted.html

@@ -327,9 +327,9 @@ up</a></li>
 <p>Note that you will need about 1-3 GB of space for a full LLVM build in Debug
 mode, depending on the system (it is so large because of all the debugging
 information and the fact that the libraries are statically linked into multiple
-tools).  If you do not need many of the tools and you are space-conscious,
-you can disable them individually in <tt>llvm/tools/Makefile</tt>.  The Release
-build requires considerably less space.</p>
+tools).  If you do not need many of the tools and you are space-conscious, you
+can pass <tt>ONLY_TOOLS="tools you need"</tt> to make.  The Release build
+requires considerably less space.</p>
 
 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
 guaranteed to do so.  If compilation is successful, the LLVM utilities should be

docs/MakefileGuide.html

@@ -841,6 +841,8 @@
     <dt><a name="MKDIR"><tt>MKDIR</tt></a><small>(defaulted)</small></dt>
     <dd>Specifies the path to the <tt>mkdir</tt> tool that creates
     directories.</dd>
+    <dt><a name="ONLY_TOOLS"><tt>ONLY_TOOLS</tt></a></dt>
+    <dd>If set, specifies the list of tools to build.</dd>
     <dt><a name="PLATFORMSTRIPOPTS"><tt>PLATFORMSTRIPOPTS</tt></a></dt>
     <dd>The options to provide to the linker to specify that a stripped (no
     symbols) executable should be built.</dd>

tools/Makefile

@@ -22,6 +22,12 @@ PARALLEL_DIRS := opt llvm-as llvm-dis \
                  lli gccas gccld llvm-extract llvm-db \
                  bugpoint llvm-bcanalyzer llvm-stub llvmc
 
+# Let users override the set of tools to build from the command line.
+ifdef ONLY_TOOLS
+  OPTIONAL_PARALLEL_DIRS :=
+  PARALLEL_DIRS := $(ONLY_TOOLS)
+endif
+
 include $(LEVEL)/Makefile.config
 
 ifeq ($(ENABLE_PIC),1)