Fix typo in the CMake setup of libFuzzer (#5136) #4132

Job	Run time
Clang_Unit_Build_Option_Tests	5m 0s
ASAN_Tests_Debug	3m 31s
Checks	5m 15s
ASAN_Tests	4m 4s
Conformance_Tests_ESNext	2m 13s
Conformance_Tests_ESNext_Debug_A	2m 15s
Conformance_Tests_ESNext_Debug_B	1m 28s
ESP_IDF_Build_Test	3m 43s
ESP8266_RTOS_SDK_Build_Test	1m 33s
Linux_AArch64_Tests	5m 1s
Linux_AArch64_Tests_Debug	7m 20s
Linux_ARMv7l_Tests	4m 23s
Linux_ARMv7l_Tests_Debug	5m 49s
Linux_x86_cpointer-32bit_Build_Correctness_Tests	1m 56s
Linux_x86-64_Build_Option_Tests	4m 49s
Linux_x86-64_Build_Correctness_Debugger_Tests	5m 1s
MbedOS_K64F_Build_Test	2m 20s
Notification	0s
NuttX_STM32F4_Build_Test	2m 39s
OSX_x86-64_Build_Correctness_Unit_Tests	2m 47s
OSX_x86-64_Build_Correctness_Unit_Tests_Debug	3m 3s
RIOT_STM32F4_Build_Test	2m 40s
UBSAN_Tests	2m 43s
Unit_Tests	1m 49s
Zephyr_STM32F4_Build_Test	4m 36s
	1h 25m 58s

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