[edk2-platforms PATCH 1/1] Readme.md: update outdated info about building BaseTools in parallel

["Rebecca Cran" <rebecca@bsdio.com>]

edk2 commit 9e1131b70b4b6002cd1904401946ef0b22cf7d33 fixed the
dependencies in the BaseTools GNUMakefile to allow the build to be
run with multiple threads.

Update Readme.md to provide an example of building with "-j4".

Signed-off-by: Rebecca Cran <rebecca@bsdio.com>
---
 Readme.md | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/Readme.md b/Readme.md
index 62876b4b7d75..cd0db9bfcb2c 100644
--- a/Readme.md
+++ b/Readme.md
@@ -115,11 +115,10 @@ target-specific binutils. These are included with any prepackaged GCC toolchain
    (This step _depends_ on **WORKSPACE** being set as per above.)
 1. Build BaseTools
 
-   `make -C edk2/BaseTools`
+   `make -j4 -C edk2/BaseTools`
 
-   (BaseTools can currently not be built in parallel, so do not specify any `-j`
-   option, either on the command line or in a **MAKEFLAGS** environment
-   variable.)
+`-j4` runs the build with 4 threads. You may change it to specify an
+appropriate value for the number of available threads.
 
 ### Build options
 There are a number of options that can (or must) be specified at the point of
-- 
2.34.0