[make][buildall] add ability to filter buildall by architecture

Clean up make targets list-arch and list-toolchain to be much faster and
work without needing to invoke the archtecture's arch rules.mk. This
should make it work on machines that do not have that particular
toolchain in the path.

This is setting up for using it in the github action script.

scripts/buildall

@@ -13,19 +13,22 @@ DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 
 function HELP {
     echo "help:"
-    echo "-e build with WERROR=1"
-    echo "-r also build DEBUG=0"
-    echo "-q hide output of build"
-    echo "-h for help"
+    echo "-a <arch> : build for <arch> (default: all)"
+    echo "-e        : build with WERROR=1"
+    echo "-r        : also build DEBUG=0"
+    echo "-q        : hide output of build"
+    echo "-h        : for help"
     exit 1
 }
 
 RELEASE=0
 WERROR=0
 QUIET=0
+ARCH="all"
 
-while getopts ehrq FLAG; do
+while getopts a:ehrq FLAG; do
     case $FLAG in
+        a) ARCH="$OPTARG";;
         e) WERROR=1;;
         h) HELP;;
         r) RELEASE=1;;
@@ -48,10 +51,30 @@ function log()
     fi
 }
 
-# build everything in the projects directory
-PROJECTS=$(echo project/*.mk | xargs -n1 basename | sed 's/\.mk//')
+# find all the projects in the project directory
+_PROJECTS=$(echo project/*.mk | xargs -n1 basename | sed 's/\.mk//')
 FAILED=""
 
+# If ARCH is set to all, we build for all architectures, otherwise we
+# filter projects based on the ARCH variable.
+if [ "$ARCH" != "all" ]; then
+    for p in $_PROJECTS; do
+        # Look for ARCH = <arch> in the output of make list-arch
+        PROJECT_ARCH="$(PROJECT=$p make list-arch | grep 'ARCH' | tail -1 | cut -d ' ' -f 3)"
+        if [ "$PROJECT_ARCH" == "$ARCH" ]; then
+            PROJECTS+="$p "
+        else
+            if (( !QUIET )); then
+                echo "Skipping $p, not compatible with architecture $ARCH"
+            fi
+        fi
+    done
+else
+    PROJECTS+="$_PROJECTS"
+fi
+
+echo projects to build: "$PROJECTS"
+
 if (( WERROR )); then
     WERROR_MSG="with WERROR"
 fi
@@ -73,4 +96,5 @@ if [ "$FAILED" != "" ]; then
     echo
     echo some projects have failed to build:
     echo "$FAILED"
+    exit 1
 fi