Update the configuration for Travis CI and AppVeyor CI

Update the Travis CI matrix:
 * Run ASan and UBSan unconditionally on FreeBSD and Linux, and
   not at all on Mac.
 * Remove the `CI_NO_TEST=1` runs from the environment column.

Update the AppVeyor CI matrix:
 * Replace `CI_NO_TEST=1` with `CI_CMAKE_VARS=-DPNG_TESTS=0` when
   testing Visual Studio on ARM64.

Also apply minor stylistic changes.
diff --git a/.appveyor.yml b/.appveyor.yml
index b850d02..e07b932 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -20,7 +20,6 @@
     - TOOLCHAIN: vstudio
       AUTOMATION: cmake
       ARCH: arm64
-      CI_NO_TEST: 1
     - TOOLCHAIN: llvm
       AUTOMATION: cmake
       ARCH: x64
@@ -55,6 +54,7 @@
   - 'if "%TOOLCHAIN%"=="vstudio" if "%ARCH%"=="x86" set CI_CMAKE_GENERATOR_PLATFORM=Win32'
   - 'if "%TOOLCHAIN%"=="vstudio" if "%ARCH%"=="x64" set CI_CMAKE_GENERATOR_PLATFORM=x64'
   - 'if "%TOOLCHAIN%"=="vstudio" if "%ARCH%"=="arm64" set CI_CMAKE_GENERATOR_PLATFORM=ARM64'
+  - 'if "%TOOLCHAIN%"=="vstudio" if "%ARCH%"=="arm64" set CI_CMAKE_VARS=-DPNG_TESTS=0'
   - 'if "%TOOLCHAIN%"=="llvm" set CI_CMAKE_GENERATOR=Ninja'
   - 'if "%TOOLCHAIN%"=="llvm" set CI_CMAKE_TOOLCHAIN_FILE=C:\tools\vcpkg\scripts\buildsystems\vcpkg.cmake'
   - 'if "%TOOLCHAIN%"=="llvm" set CI_CC=clang.exe'
@@ -62,8 +62,8 @@
   - 'if "%TOOLCHAIN%"=="msys2" if "%ARCH%"=="i686" set PATH=C:\msys64\mingw32\bin;%PATH%'
   - 'if "%TOOLCHAIN%"=="msys2" if "%ARCH%"=="x86_64" set PATH=C:\msys64\mingw64\bin;%PATH%'
   - 'if "%TOOLCHAIN%"=="msys2" set CI_CC=%ARCH%-w64-mingw32-gcc.exe'
-  - 'set CI_CMAKE_BUILD_FLAGS=--parallel 2'
-  - 'set CI_CTEST_FLAGS=--parallel 2'
+  - 'set CI_CMAKE_BUILD_FLAGS=-j2'
+  - 'set CI_CTEST_FLAGS=-j2'
   - 'set CI_MAKE_FLAGS=-j2'
   - 'set CI_MAKEFILES=scripts/makefile.gcc scripts/makefile.msys scripts/makefile.std'
 
diff --git a/.travis.yml b/.travis.yml
index dfbefa7..ab3fba6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -10,14 +10,11 @@
   - osx
 
 env:
-  - AUTOMATION=cmake CI_NO_TEST=1
-  - AUTOMATION=cmake CI_CMAKE_VARS="-DPNG_HARDWARE_OPTIMIZATIONS=ON" CI_SANITIZERS="address,undefined"
-  - AUTOMATION=cmake CI_CMAKE_VARS="-DPNG_HARDWARE_OPTIMIZATIONS=OFF" CI_SANITIZERS="address,undefined"
-  - AUTOMATION=configure CI_NO_TEST=1
+  - AUTOMATION=cmake CI_CMAKE_VARS="-DPNG_HARDWARE_OPTIMIZATIONS=ON"
+  - AUTOMATION=cmake CI_CMAKE_VARS="-DPNG_HARDWARE_OPTIMIZATIONS=OFF"
   - AUTOMATION=configure CI_CONFIGURE_FLAGS="--enable-hardware-optimizations"
   - AUTOMATION=configure CI_CONFIGURE_FLAGS="--disable-hardware-optimizations"
-  - AUTOMATION=makefiles CI_NO_TEST=1
-  - AUTOMATION=makefiles CI_SANITIZERS="address,undefined"
+  - AUTOMATION=makefiles
 
 matrix:
   include:
@@ -25,11 +22,12 @@
       env: AUTOMATION=cmake CI_CMAKE_GENERATOR=Xcode
 
 before_script:
-  - 'if test "$TRAVIS_OS_NAME" = "linux"; then COMPILER="gcc"; else COMPILER="clang"; fi'
-  - 'export CI_MAKEFILES="scripts/makefile.std scripts/makefile.$COMPILER"'
-  - 'export CI_MAKE_FLAGS="-j2"'
-  - 'export CI_CMAKE_BUILD_FLAGS="--parallel 2"'
-  - 'export CI_CTEST_FLAGS="--parallel 2"'
+  - 'if test "$TRAVIS_OS_NAME" = "linux"; then export CI_CC="gcc"; else export CI_CC="clang"; fi'
+  - 'if test "$TRAVIS_OS_NAME" != "osx"; then export CI_SANITIZERS="address,undefined"; fi'
+  - 'export CI_MAKEFILES="scripts/makefile.$CI_CC scripts/makefile.std"'
+  - 'export CI_MAKE_FLAGS=-j2'
+  - 'export CI_CMAKE_BUILD_FLAGS=-j2'
+  - 'export CI_CTEST_FLAGS=-j2'
 
 script:
   - './ci/ci_verify_$AUTOMATION.sh'