[lldb][docs] Add CMake version notes for -B flag

The original documentation update was reviewed with D65330

llvm-svn: 367407

lldb/docs/_static/lldb.css

@@ -10,6 +10,14 @@ div.body {
   max-width: 90%;
 }
 
+div.note {
+  padding: 20px 20px 10px 20px;
+}
+
+div.note p.admonition-title {
+  font-size: 130%;
+}
+
 table.mapping {
   width: 100%;
 }

lldb/docs/resources/build.rst

@@ -125,10 +125,10 @@ checked out above, but now we will have two build-trees:
 * the main build-tree for LLDB in ``/path/to/lldb-build``
 * a provided build-tree for LLVM and Clang in ``/path/to/llvm-build``
 
-Run CMake with ``-B`` pointing to a new directory for the provided build-tree
-and the positional argument pointing to the ``llvm`` directory in the
-source-tree. Note that we leave out LLDB here and only include Clang.
-Then we build the ``ALL`` target with ninja:
+Run CMake with ``-B`` pointing to a new directory for the provided
+build-tree\ :sup:`1` and the positional argument pointing to the ``llvm``
+directory in the source-tree. Note that we leave out LLDB here and only include
+Clang. Then we build the ``ALL`` target with ninja:
 
 ::
 
@@ -151,6 +151,11 @@ case-sensitive!):
           [<more cmake options>] /path/to/llvm-project/lldb
   > ninja lldb
 
+.. note::
+
+   #. The ``-B`` argument was undocumented for a while and is only officially
+      supported since `CMake version 3.14
+      <https://cmake.org/cmake/help/v3.14/release/3.14.html#command-line>`_
 
 .. _CommonCMakeOptions:
 
@@ -321,6 +326,12 @@ Build LLDB standalone for development with Xcode:
   > open lldb.xcodeproj
   > cmake --build /path/to/lldb-build --target check-lldb
 
+.. note::
+
+   The ``-B`` argument was undocumented for a while and is only officially
+   supported since `CMake version 3.14
+   <https://cmake.org/cmake/help/v3.14/release/3.14.html#command-line>`_
+
 
 Building The Documentation
 --------------------------