contrib: soxr: don't force the CMAKE_SYSTEM_NAME when cross compiling

The proper value is already set in the toolchain.cmake since a6dcec33.
If the value is not set for a cross compiled target, building fails since f2e67d22.

contrib/src/soxr/rules.mak

@@ -27,16 +27,7 @@ soxr: soxr-$(SOXR_VERSION)-Source.tar.xz .sum-soxr
 	$(call pkg_static,"src/soxr.pc.in")
 	$(MOVE)
 
-# CMAKE_SYSTEM_NAME is inferred from the toolchain in Android builds
-ifndef HAVE_ANDROID
-# Force CMAKE_CROSSCOMPILING to True
-ifdef HAVE_CROSS_COMPILE
-SOXR_EXTRA_CONF=-DCMAKE_SYSTEM_NAME=Generic
-endif
-endif
-
 SOXR_CONF := \
-		$(SOXR_EXTRA_CONF) \
 		-DBUILD_TESTS=OFF \
 		-DWITH_LSR_BINDINGS=OFF \
 		-DWITH_OPENMP=OFF \