Fix typo in the CMake setup of libFuzzer #4131

Job	Run time
Clang_Unit_Build_Option_Tests	4m 28s
ASAN_Tests	3m 38s
ASAN_Tests_Debug	3m 55s
Checks	5m 19s
Conformance_Tests_ESNext	2m 14s
Conformance_Tests_ESNext_Debug_A	2m 8s
Conformance_Tests_ESNext_Debug_B	1m 20s
ESP_IDF_Build_Test	3m 19s
ESP8266_RTOS_SDK_Build_Test	1m 40s
Linux_AArch64_Tests	4m 28s
Linux_AArch64_Tests_Debug	6m 28s
Linux_ARMv7l_Tests	4m 24s
Linux_ARMv7l_Tests_Debug	5m 57s
Linux_x86-64_Build_Correctness_Debugger_Tests	5m 15s
Linux_x86_cpointer-32bit_Build_Correctness_Tests	2m 29s
Linux_x86-64_Build_Option_Tests	4m 25s
MbedOS_K64F_Build_Test	1m 52s
Notification	0s
NuttX_STM32F4_Build_Test	2m 0s
OSX_x86-64_Build_Correctness_Unit_Tests	2m 44s
OSX_x86-64_Build_Correctness_Unit_Tests_Debug	4m 24s
RIOT_STM32F4_Build_Test	1m 4s
UBSAN_Tests	2m 16s
Unit_Tests	1m 49s
Zephyr_STM32F4_Build_Test	2m 59s
	1h 20m 35s

Provide feedback