qmake 语法：+= 与 *=（加号与星号）
qmake syntax: += vs. *= (plus vs. asterisk)
以下语句在 .pro 文件中使用加号与星号有什么区别？：
LIBS *= -lz
对比
LIBS += -lz
The *= operator adds a value to the list of values in a variable, but only if it is not already present. This prevents values from being included many times in a variable.
以下语句在 .pro 文件中使用加号与星号有什么区别？：
LIBS *= -lz
对比
LIBS += -lz
The
*=operator adds a value to the list of values in a variable, but only if it is not already present. This prevents values from being included many times in a variable.