title: Configuring qtbase fails with an error: "Could not find qmake spec ''."
body: <p>I am trying to cross-compile qtbase-everywhere-5.11.0 for the Raspberry Pi 3 and configure phase exits after the qmake compilation with the error given below:</p>
  
  <pre><code>make: Nothing to be done for 'first'.
  Could not find qmake spec ''.
  Error processing project file: /work/qtbase-everywhere-src-5.11.0
  </code></pre>
  
  <p>I do it inside a docker container. Here is the <code>Dockerfile</code></p>
  
  <pre><code>FROM ubuntu:18.04
  
  COPY sources.list /etc/apt/
  
  RUN apt update -q -yy &amp;&amp; \
      apt upgrade -q -yy &amp;&amp; \
      apt install -q -yy aptitude curl
  
  RUN dpkg --add-architecture armhf
  
  RUN apt install -q -yy --allow-downgrades \
          build-essential \
          linux-libc-dev:armhf=4.15.0-20.21 linux-libc-dev:amd64=4.15.0-20.21 \
          crossbuild-essential-armhf \
          libncurses5:amd64=6.1-1ubuntu1 \
          libncursesw5:amd64=6.1-1ubuntu1 \
          libtinfo5:amd64=6.1-1ubuntu1 \
          libgles2-mesa-dev:armhf \
          libpcre3-dev:armhf \
          libasound2-dev:armhf \
          libasound2-data=1.1.3-5
  </code></pre>
  
  <p>and the <code>configure</code> arguments</p>
  
  <pre><code>configure \
       -device linux-rasp-pi3-g++ \
       -examplesdir /usr/lib/qt/examples \
       -headerdir /usr/include/qt5 \
       -no-rpath \
       -nomake tests \
       -plugindir /usr/lib/qt/plugins \
       -prefix /usr \
       -v \
       -confirm-license \
       -eglfs \
       -no-cups \
       -no-iconv \
       -no-kms \
       -no-pch \
       -no-use-gold-linker \
       -no-xcb \
       -no-sql-sqlite \
       -no-sql-mysql \
       -no-sql-psql \
       -no-sql-tds \
       -no-sql-odbc \
       -no-linuxfb \
       -no-widgets \
       -opengl es2 \
       -opensource \
       -release \
       -shared \
       -system-zlib \
       -device-option CROSS_COMPILE=/usr/bin/arm-linux-gnueabihf-
  </code></pre>
  
  <p>I realized that configuring it with default parameters doesn't work either. Running just <code>./configure -v</code> inside a source directory gives the same error. </p>
  
  <p>I found that it doesn't happen when I am building using <code>dockcross/linux-armhf7</code> based docker image.</p>