Allow custom builddir with compile_cmake

satellites/functions/compile/cmake.sh

@@ -1,17 +1,19 @@
 compile_cmake() {
     local olddir="$PWD"
+    local builddir='build'
     local noinstall=false
 
     local OPTIND=1
     local opt
-    while getopts 'I' opt; do case "$opt" in
+    while getopts 'b:I' opt; do case "$opt" in
+        b) local builddir="$OPTARG" ;;
         I) local noinstall=true ;;
     esac; done
     shift $((OPTIND-1))
     [ "$1" = '--' ] && shift
 
-    mkdir -p build; cd build
-    cmake .. \
+    mkdir -p "$builddir"; cd "$builddir"
+    cmake "$olddir" \
         -DCMAKE_BUILD_TYPE=Release \
         -DCMAKE_INSTALL_PREFIX="/$dir_prefix" \
         -DCMAKE_INSTALL_SYSCONFDIR="$dir_sysconfdir" \