Install OpenMP to sysroot (#1541)

Or we can't find headers and libraries.

Author: wangpc-pp

Makefile.in

@@ -1016,7 +1016,7 @@ stamps/build-llvm-linux: $(LLVM_SRCDIR) $(LLVM_SRC_GIT) $(BINUTILS_SRCDIR) $(BIN
 	    mkdir $(notdir $@)/openmp-shared; \
 	    cmake -S$(LLVM_SRCDIR)/openmp \
 	        -B$(notdir $@)/openmp-shared \
-	        -DCMAKE_INSTALL_PREFIX=$(INSTALL_DIR) \
+	        -DCMAKE_INSTALL_PREFIX=$(SYSROOT) \
 	        -DCMAKE_C_COMPILER=$(INSTALL_DIR)/bin/clang \
 	        -DCMAKE_CXX_COMPILER=$(INSTALL_DIR)/bin/clang++ \
 	        -DOPENMP_ENABLE_LIBOMPTARGET=Off \
@@ -1035,7 +1035,7 @@ stamps/build-llvm-linux: $(LLVM_SRCDIR) $(LLVM_SRC_GIT) $(BINUTILS_SRCDIR) $(BIN
 	    mkdir $(notdir $@)/openmp-static; \
 	    cmake -S$(LLVM_SRCDIR)/openmp \
 	        -B$(notdir $@)/openmp-static \
-	        -DCMAKE_INSTALL_PREFIX=$(INSTALL_DIR) \
+	        -DCMAKE_INSTALL_PREFIX=$(SYSROOT) \
 	        -DCMAKE_C_COMPILER=$(INSTALL_DIR)/bin/clang \
 	        -DCMAKE_CXX_COMPILER=$(INSTALL_DIR)/bin/clang++ \
 	        -DOPENMP_ENABLE_LIBOMPTARGET=Off \