Mine

Running "make -f Makefile CONF=Release" in /home/evil/Test

make -f nbproject/Makefile-Release.mk SUBPROJECTS= .build-conf
make[1]: Entering directory `/home/evil/Test'
mkdir -p build/Release/GNU-Linux-x86
gcc    -c -O2 -o build/Release/GNU-Linux-x86/Test.o Test.c
mkdir -p dist/Release/GNU-Linux-x86
gcc     -o dist/Release/GNU-Linux-x86/test build/Release/GNU-Linux-x86/Test.o  
build/Release/GNU-Linux-x86/Test.o: In function `main':
Test.c:(.text+0x39): undefined reference to `pthread_attr_setstacksize'
Test.c:(.text+0x58): undefined reference to `pthread_create'
Test.c:(.text+0x6a): undefined reference to `pthread_join'
collect2: ld returned 1 exit status
make[1]: *** [dist/Release/GNU-Linux-x86/test] Error 1
make[1]: Leaving directory `/home/evil/Test'
make: *** [.build-impl] Error 2

Build failed. Exit value 2.