misc: Updated the RELEASE-NOTES and version number

Updated the RELEASE-NOTES.md and version number for the v20.1.0.4
hotfix release.

Change-Id: Iaefed86cb176c3adcd66d101ac3155d30528b025
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/41713
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
diff --git a/RELEASE-NOTES.md b/RELEASE-NOTES.md
index c84d9b4..3f17091 100644
@@ -1,3 +1,8 @@
+# Version
+**[HOTFIX]** [gem5 was failing to build with SCons 4.0.1 and 4.1.0](https://gem5.atlassian.net/browse/GEM5-916).
+This hotfix makes the necessary changes to `site_scons/site_tools/default.py` for gem5 to compile successfully on these versions of SCons.
 # Version
 **[HOTFIX]** A patch was apply to fix an [error where booting Linux stalled when using the ARM ISA](https://gem5.atlassian.net/browse/GEM5-901).
diff --git a/src/Doxyfile b/src/Doxyfile
index ddc3933..4ad0ea5 100644
--- a/src/Doxyfile
+++ b/src/Doxyfile
@@ -31,7 +31,7 @@
 # This could be handy for archiving the generated documentation or 
 # if some version control system is used.
-PROJECT_NUMBER         = v20.1.0.3
+PROJECT_NUMBER         = v20.1.0.4
 # The OUTPUT_DIRECTORY tag is used to specify the (relative or absolute) 
 # base path where the generated documentation will be put. 
diff --git a/src/base/version.cc b/src/base/version.cc
index d30ddd1..0a34488 100644
--- a/src/base/version.cc
+++ b/src/base/version.cc
@@ -29,4 +29,4 @@
  * @ingroup api_base_utils
-const char *gem5Version = "";
+const char *gem5Version = "";