[docs] Update docs for cmake options LLDB_TEST_C_COMPILER and LLDB_TEST_CXX_COMPILER

[asmith]

Summary

LLDB_TEST_COMPILER is not a valid option for CMake for LLDB. There are instead two properties LLDB_TEST_C_COMPILER and LLDB_TEST_CXX_COMPILER. Update the documents accordingly to reflect the correct information.

lldb/trunk/www/build.html

<div id="content">
                 <b>LLDB_RELOCATABLE_PYTHON</b> (Default=0): When this is 0, LLDB will bind statically to the location specified
                 in the PYTHON_HOME CMake variable, ignoring any value of PYTHONHOME set in the environment.  This is most useful for
                 developers who simply want to run LLDB after they build it.  If you wish to move a build of LLDB to a different
                 machine where Python will be in a different location, setting LLDB_RELOCATABLE_PYTHON to 1 will cause Python to
                 use its default mechanism for finding the python installation at runtime (looking for installed Pythons, or using
                 the PYTHONHOME environment variable if it is specified).
               </li>
               <li>
-                <b>LLDB_TEST_COMPILER</b>: The test suite needs to be able to find a copy of clang.exe that it can use to compile
-                inferior programs.  Note that MSVC is not supported here, it <strong>must</strong> be a path to a clang executable.
-                Note that using a release clang.exe is strongly recommended here, as it will make the test suite run much faster.
+                <b>LLDB_TEST_C_COMPILER</b> or <b>LLDB_TEST_CXX_COMPILER</b>: The test suite needs to be able to find a copy of clang.exe
+                that it can use to compile inferior programs.  Note that MSVC is not supported here, it <strong>must</strong> be a path to a
+                clang executable.  Note that using a release clang.exe is strongly recommended here, as it will make the test suite run much faster.
                 This can be a path to any recent clang.exe, including one you built yourself.
               </li>
             </ul>
             Sample command line:<br/>
-            <code>cmake -G Ninja -DLLDB_TEST_DEBUG_TEST_CRASHES=1 -DPYTHON_HOME=C:\Python35 -DLLDB_TEST_COMPILER=d:\src\llvmbuild\ninja_release\bin\clang.exe ..\..\llvm</code>
+            <code>cmake -G Ninja -DLLDB_TEST_DEBUG_TEST_CRASHES=1 -DPYTHON_HOME=C:\Python35 -DLLDB_TEST_C_COMPILER=d:\src\llvmbuild\ninja_release\bin\clang.exe ..\..\llvm</code>
             <h2>Working with both Ninja and MSVC</h2>
             <p>
               Compiling with <code>ninja</code> is both faster and simpler than compiling with MSVC, but chances are you still want
               to debug LLDB with MSVC (at least until we can debug LLDB on Windows with LLDB!).  One solution to this is to run 
               <code>cmake</code> twice and generate the output into two different folders.  One for compiling (the <code>ninja</code>
               folder), and one for editing / browsing / debugging (the MSVC folder).
             </p>
             <p>

lldb/trunk/www/test.html

<div id="content">
               <strong>Windows Note</strong>: In the examples that follow, any invocations of <code>python</code>
               should be replaced with <code>python_d</code>, the debug interpreter, when running the test
               suite against a debug version of LLDB.
             </p>
             <p>
               The easiest way to run the LLDB test suite is to use the <tt>check-lldb</tt> build
               target. By default, the <tt>check-lldb</tt> target builds the test programs with
               the same compiler that was used to build LLDB. To build the tests with a different
-              compiler, you can set the <strong>LLDB_TEST_COMPILER</strong> CMake variable. It is possible to
-              customize the architecture of the test binaries and compiler used by appending -A
+              compiler, you can set the <strong>LLDB_TEST_C_COMPILER</strong> or the <strong>LLDB_TEST_CXX_COMPILER</strong> CMake variables.
+              It is possible to customize the architecture of the test binaries and compiler used by appending -A
               and -C options respectively to the CMake variable <strong>LLDB_TEST_USER_ARGS</strong>. For
               example, to test LLDB against 32-bit binaries
               built with a custom version of clang, do:
             </p>
             <code>
               <br />&gt; cmake -DLLDB_TEST_USER_ARGS="-A i386 -C /path/to/custom/clang" -G Ninja
               <br />&gt; ninja check-lldb
             </code>