bash uses curly braces

Change-Id: I2799c766008dc9016d2e55e6e40ae2c4ae4b37d2
diff --git a/build/make/configure.sh b/build/make/configure.sh
index b5ba4a9..0f6c6ca 100755
--- a/build/make/configure.sh
+++ b/build/make/configure.sh
@@ -1150,7 +1150,7 @@
     fi
 
     # only for MIPS platforms
-    case $(toolchain) in
+    case ${toolchain} in
         mips*)
             if enabled dspr2; then
                 if enabled big_endian; then