[Mod] change build sequence

.travis.yml

@@ -51,23 +51,6 @@ matrix:
         - pip install -r requirements.txt
         - pip install .
 
-    - name: "pip install under Ubuntu: gcc-8"
-      before_install:
-        # C++17
-        - sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
-        - sudo apt-get update -y
-      install:
-        # C++17
-        - sudo apt-get install -y gcc-8 g++-8
-        - sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-8 90
-        - sudo update-alternatives --install /usr/bin/c++ c++ /usr/bin/g++-8 90
-        - sudo update-alternatives --install /usr/bin/gcc cc /usr/bin/gcc-8 90
-        # update pip & setuptools
-        - python -m pip install --upgrade pip wheel setuptools
-        # Linux install script
-        - pip install https://pip.vnpy.com/colletion/ibapi-9.75.1-001-py3-none-any.whl
-        - bash ./install.sh
-
     - name: "pip install under Ubuntu: gcc-7"
       before_install:
         # C++17
@@ -92,6 +75,23 @@ matrix:
         - pip3 install https://pip.vnpy.com/colletion/ibapi-9.75.1-001-py3-none-any.whl
         - bash ./install.sh python3 pip3
 
+    - name: "pip install under Ubuntu: gcc-8"
+      before_install:
+        # C++17
+        - sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
+        - sudo apt-get update -y
+      install:
+        # C++17
+        - sudo apt-get install -y gcc-8 g++-8
+        - sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-8 90
+        - sudo update-alternatives --install /usr/bin/c++ c++ /usr/bin/g++-8 90
+        - sudo update-alternatives --install /usr/bin/gcc cc /usr/bin/gcc-8 90
+        # update pip & setuptools
+        - python -m pip install --upgrade pip wheel setuptools
+        # Linux install script
+        - pip install https://pip.vnpy.com/colletion/ibapi-9.75.1-001-py3-none-any.whl
+        - bash ./install.sh
+
     - name: "sdist install under Windows"
       os: "windows"
       services: []  # service is not need