$ make build-example

make -C simavr RELEASE=0
make[1]: Entering directory '/tmp/simavr/simavr'
make obj config
make[2]: Entering directory '/tmp/simavr/simavr'
make[2]: Nothing to be done for 'obj'.
make[2]: Nothing to be done for 'config'.
make[2]: Leaving directory '/tmp/simavr/simavr'
make libsimavr run_avr
make[2]: Entering directory '/tmp/simavr/simavr'
make[2]: Nothing to be done for 'libsimavr'.
LD obj-x86_64-pc-linux-gnu/run_avr.elf
ln -sf obj-x86_64-pc-linux-gnu/run_avr.elf run_avr
make[2]: Leaving directory '/tmp/simavr/simavr'
make[1]: Leaving directory '/tmp/simavr/simavr'
make -C examples RELEASE=0
make[1]: Entering directory '/tmp/simavr/examples'
for bi in board_ds1338 board_hd44780 board_i2ctest board_ledramp board_rotenc board_simduino board_ssd1306 board_timer_64led; do make -C $bi; done
make[2]: Entering directory '/tmp/simavr/examples/board_ds1338'
ds1338demo done
make[2]: Leaving directory '/tmp/simavr/examples/board_ds1338'
make[2]: Entering directory '/tmp/simavr/examples/board_hd44780'
LD obj-x86_64-pc-linux-gnu/charlcd.elf
/usr/bin/ld: obj-x86_64-pc-linux-gnu/hd44780_glut.o: undefined reference to symbol 'glEnable'
/usr/bin/ld: /usr/lib/libOpenGL.so.0: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
make[2]: *** [../..//Makefile.common:193: obj-x86_64-pc-linux-gnu/charlcd.elf] Error 1
make[2]: Leaving directory '/tmp/simavr/examples/board_hd44780'
make[2]: Entering directory '/tmp/simavr/examples/board_i2ctest'
i2ctest done
make[2]: Leaving directory '/tmp/simavr/examples/board_i2ctest'
make[2]: Entering directory '/tmp/simavr/examples/board_ledramp'
LD obj-x86_64-pc-linux-gnu/ledramp.elf
/usr/bin/ld: obj-x86_64-pc-linux-gnu/ledramp.o: undefined reference to symbol 'glEnd'
/usr/bin/ld: /usr/lib/libOpenGL.so.0: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
make[2]: *** [../..//Makefile.common:193: obj-x86_64-pc-linux-gnu/ledramp.elf] Error 1
make[2]: Leaving directory '/tmp/simavr/examples/board_ledramp'
make[2]: Entering directory '/tmp/simavr/examples/board_rotenc'
LD obj-x86_64-pc-linux-gnu/rotenc_test.elf
/usr/bin/ld: obj-x86_64-pc-linux-gnu/rotenc_test.o: undefined reference to symbol 'glEnd'
/usr/bin/ld: /usr/lib/libOpenGL.so.0: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
make[2]: *** [../../Makefile.common:193: obj-x86_64-pc-linux-gnu/rotenc_test.elf] Error 1
make[2]: Leaving directory '/tmp/simavr/examples/board_rotenc'
make[2]: Entering directory '/tmp/simavr/examples/board_simduino'
simduino done
make[2]: Leaving directory '/tmp/simavr/examples/board_simduino'
make[2]: Entering directory '/tmp/simavr/examples/board_ssd1306'
LD obj-x86_64-pc-linux-gnu/ssd1306demo.elf
/usr/bin/ld: obj-x86_64-pc-linux-gnu/ssd1306_glut.o: undefined reference to symbol 'glEnable'
/usr/bin/ld: /usr/lib/libOpenGL.so.0: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
make[2]: *** [../..//Makefile.common:193: obj-x86_64-pc-linux-gnu/ssd1306demo.elf] Error 1
make[2]: Leaving directory '/tmp/simavr/examples/board_ssd1306'
make[2]: Entering directory '/tmp/simavr/examples/board_timer_64led'
LD obj-x86_64-pc-linux-gnu/timer_64led.elf
/usr/bin/ld: obj-x86_64-pc-linux-gnu/timer_64led.o: undefined reference to symbol 'glEnd'
/usr/bin/ld: /usr/lib/libOpenGL.so.0: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
make[2]: *** [../..//Makefile.common:193: obj-x86_64-pc-linux-gnu/timer_64led.elf] Error 1
make[2]: Leaving directory '/tmp/simavr/examples/board_timer_64led'
make[1]: *** [Makefile:11: all] Error 2
make[1]: Leaving directory '/tmp/simavr/examples'
make: *** [Makefile:24: build-examples] Error 2