Fix MINGW_ROOT variable value computation when not being provided.

.travis.yml

@@ -53,7 +53,7 @@ install:
     - sudo apt-get install -q -y --no-install-recommends libasound2-dev
     - bash -c "[ x$ENABLE_64BIT == 'x' ]" && sudo apt-get remove -q -y gvfs-daemons && sudo apt-get install -q -y libxrandr-dev:i386 libgl1-mesa-dev:i386 libxext-dev:i386 libxrender-dev:i386 g++-multilib && export CMAKE_PREFIX_PATH=/usr/lib/i386-linux-gnu || true
     - bash -c "( [ $SITE_UPDATE_ON_MASTER_COMMIT ] || [ $PACKAGE_UPLOAD ] )" && sudo apt-get install -q -y --no-install-recommends doxygen graphviz || true
-    - bash -c "[ $WINDOWS ]" && sudo apt-get install -q -y gcc-mingw-w64 gcc-mingw-w64-i686 gcc-mingw-w64-x86-64 g++-mingw-w64 g++-mingw-w64-i686 g++-mingw-w64-x86-64 binutils-mingw-w64 binutils-mingw-w64-i686 binutils-mingw-w64-x86-64 && export MINGW_PREFIX=/usr/bin/${ARCH}-w64 MINGW_ROOT=/usr/${ARCH}-w64-mingw32 || true
+    - bash -c "[ $WINDOWS ]" && sudo apt-get install -q -y gcc-mingw-w64 gcc-mingw-w64-i686 gcc-mingw-w64-x86-64 g++-mingw-w64 g++-mingw-w64-i686 g++-mingw-w64-x86-64 binutils-mingw-w64 binutils-mingw-w64-i686 binutils-mingw-w64-x86-64 && export MINGW_PREFIX=/usr/bin/${ARCH}-w64-mingw32 || true
     - bash -c "[ $LINUX ] && [ $PACKAGE_UPLOAD ]" && sudo apt-get install -q -y rpm || true
     - bash -e /etc/init.d/xvfb start
 script: rake travis_ci

Source/CMake/Toolchains/mingw.toolchain.cmake

@@ -34,14 +34,15 @@ set (CMAKE_SYSTEM_PROCESSOR x86)
 file (TO_CMAKE_PATH "$ENV{MINGW_PREFIX}" MINGW_PREFIX)
 
 # C/C++ compilers
-set (CMAKE_C_COMPILER ${MINGW_PREFIX}-mingw32-gcc      CACHE PATH "C compiler")
-set (CMAKE_CXX_COMPILER ${MINGW_PREFIX}-mingw32-g++    CACHE PATH "C++ compiler")
-set (CMAKE_RC_COMPILER ${MINGW_PREFIX}-mingw32-windres CACHE PATH "RC compiler")
+set (CMAKE_C_COMPILER ${MINGW_PREFIX}-gcc      CACHE PATH "C compiler")
+set (CMAKE_CXX_COMPILER ${MINGW_PREFIX}-g++    CACHE PATH "C++ compiler")
+set (CMAKE_RC_COMPILER ${MINGW_PREFIX}-windres CACHE PATH "RC compiler")
 
 # specify the system root
 file (TO_CMAKE_PATH "$ENV{MINGW_ROOT}" MINGW_ROOT)
 if (NOT MINGW_ROOT)
-    set (MINGW_ROOT /usr/${MINGW_PREFIX}-mingw32)
+    get_filename_component (MINGW_PREFIX ${MINGW_PREFIX} NAME)
+    set (MINGW_ROOT /usr/${MINGW_PREFIX}/sys-root/mingw)
 endif ()
 set (MINGW_SYSROOT ${MINGW_ROOT} CACHE PATH "Path to MinGW SYSROOT")
 set (CMAKE_FIND_ROOT_PATH ${MINGW_SYSROOT})