GP4 on a PIC12F683 microcontroller not functioning correctly
This chip has so many functions multiplexed on that one pin, that you must work hard to configure it as GP4 digital output.
It appears that your config line #pragma config FOSC = EXTRCCLK forces that GP4 pin to be a clock output, and disables digital output function. As @brhans has suggested, look at the compilers config output to verify. In the diagram below, CLKOUT appears to be derived from CONFIG:


You have properly disabled Analog Input mode for the Analog-to-digital and CMCON1 seems proper. It might be wise to add:

CMCON1 = 0b00000000;