Escape PKG_CHECK_MODULES

[catap]

This small changes allows to fix an issues avast/retdec#990 and probably #1171

The root cause of this issues is different shell which is used. Some simple shell like dsh I belive can't survive on this line without escaping, some modern like bash easly can.

Thus at § 3.5 at https://autotools.io/pkgconfig/pkg_check_modules.html it is cleare suggested to escape by [...].

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[catap]

@googlebot I signed it!