Ask for a confirmation before initiating the build.

Although it is mentioned in http://phantomjs.org/build.html, many people
are not aware this, they compile from source (even if a binary package
is available) and get shocked to realize the build takes ages.
The build script is thus modified to give the initial warning.

Unattended build is still possible, just use --confirm flag.

http://code.google.com/p/phantomjs/issues/detail?id=862

build.sh

@@ -4,6 +4,7 @@ set -e
 
 QT_CFG=''
 
+BUILD_CONFIRM=0
 COMPILE_JOBS=1
 MAKEFLAGS_JOBS=''
 
@@ -43,9 +44,13 @@ until [ -z "$1" ]; do
             shift
             COMPILE_JOBS=$1
             shift;;
+        "--confirm")
+            BUILD_CONFIRM=1
+            shift;;
         "--help")
             echo "Usage: $0 [--qt-config CONFIG] [--jobs NUM]"
             echo
+            echo "  --confirm                   Silently confirm the build."
             echo "  --qt-config CONFIG          Specify extra config options to be used when configuring Qt"
             echo "  --jobs NUM                  How many parallel compile jobs to use. Defaults to 4."
             echo
@@ -57,6 +62,30 @@ until [ -z "$1" ]; do
     esac
 done
 
+
+if [[ "$BUILD_CONFIRM" -eq 0 ]]; then
+cat << EOF
+----------------------------------------
+               WARNING
+----------------------------------------
+
+Building PhantomJS from source takes a very long time, anywhere from 30 minutes
+to several hours (depending on the machine configuration). It is recommended to
+use the premade binary packages on supported operating systems.
+
+For details, please go the the web site: http://phantomjs.org/download.html.
+
+EOF
+
+    echo "Do you want to continue (y/n)?"
+    read continue
+    if [[ "$continue" != "y" ]]; then
+        exit 1
+    fi
+    echo
+    echo
+fi
+
 cd src/qt && ./preconfig.sh --jobs $COMPILE_JOBS --qt-config "$QT_CFG" && cd ../..
 src/qt/bin/qmake $QMAKE_ARGS
 make -j$COMPILE_JOBS

deploy/build-and-package.sh

@@ -11,7 +11,7 @@ echo
 # This incantation will cause Qt and WebKit and PhantomJS to all build in "release"
 # mode, with compiler optimisations, but also with debug symbols. (We will strip the
 # symbols in package.sh.)
-CFLAGS=-g CXXFLAGS=-g ./build.sh --qt-config '-webkit-debug' --qmake-args "QMAKE_CFLAGS=-g QMAKE_CXXFLAGS=-g" || exit 1
+CFLAGS=-g CXXFLAGS=-g ./build.sh --confirm --qt-config '-webkit-debug' --qmake-args "QMAKE_CFLAGS=-g QMAKE_CXXFLAGS=-g" || exit 1
 
 # Package the release tarball
 rm deploy/*.tar.bz2 2>/dev/null