[QNX] Configure doesn't detect slog2 with QNX 7.0

When the Qt 5.9.2 build is configured for QNX 7.0 on Windows host the slog2 is not detected in QNX SDK.

configure -prefix C:\QtQNX\qt5-5.9.2 -release -nomake examples -nomake tests -platform win32-g++ -xplatform qnx-armle-v7-qcc -opengl es2 -no-cups -no-iconv -skip qtlocation -skip qtconnectivity -skip qtsensors -mp -commercial -no-eglfs -qpa qnx -confirm-license OPENSSL_LIBS="-lssl -lcrypto"

Running configuration tests...
Checking for gold linker... yes
Checking for valid makespec... yes
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Checking for poll()... yes
Checking for PPS... yes
Checking for slog2... no !!!!
Checking for 64 bit atomics... yes
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Qt Core:
DoubleConversion ....................... yes
Using system DoubleConversion ........ no
GLib ................................... no
iconv .................................. no
ICU .................................... yes
Logging backends:
journald ............................. no
syslog ............................... no
slog2 ................................ no
PPS .................................... yes
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