Not everyone uses bash, so fix test syntax.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@206118 91177308-0d34-0410-b5e6-96231b3b80d8

lib/buildit

@@ -50,7 +50,7 @@ case $TRIPLE in
       RC_CFLAGS="-arch i386 -arch x86_64"
     fi
     SOEXT=dylib
-    if [ "$MACOSX_DEPLOYMENT_TARGET" == "10.6" ]
+    if [ "$MACOSX_DEPLOYMENT_TARGET" = "10.6" ]
     then
         EXTRA_FLAGS="-nostdinc++ -std=c++11 -U__STRICT_ANSI__"
         LDSHARED_FLAGS="-o libc++.1.dylib \
@@ -106,7 +106,7 @@ case $TRIPLE in
     hostOS=`echo $hostOS | sed -e "s/\s+$//"`
     hostOS=`echo $hostOS | tr '[A-Z]' '[a-z]'`
 
-    if [ $hostOS == "linux" ]
+    if [ $hostOS = "linux" ]
     then
       LDSHARED_FLAGS="-o libc++.so.1 \
         -qmkshrobj -Wl,-soname,libc++.so.1 \
@@ -158,7 +158,7 @@ case $TRIPLE in
     *-*-mingw*)
         ;;
     *-ibm-*)
-        if [ $hostOS == "linux" ]
+        if [ $hostOS = "linux" ]
         then
            rm -f libc++.so
            ln -s libc++.so.1 libc++.so