Adjust whitespace between = and OSFLAG

Signed-off-by: Daniel Lim Wee Soong <weesoong.lim@gmail.com>

docs/Makefile

diff --git a/docs/Makefile b/docs/Makefile
index 378014c..4f04031 100644
--- a/docs/Makefile
+++ b/docs/Makefile
@@ -10,7 +10,7 @@
 SPHINXPROJ      = SymbiFlowV2X
 SOURCEDIR       = .
 BUILDDIR        = _build
-OSFLAG 				:=
+OSFLAG          =
 UNAME_S := $(shell uname -s)
 ifneq (, $(findstring Linux, $(UNAME_S)))
 	OSFLAG := Linux