I know this error relates to missing TAB, but I somehow cannot find out where on line 1 is the tab missing:
Makefile:
## -*- mode: make; tab-width: 8; -*-
##
## Simple Makefile
##
## TODO:
## proper configure for non-Debian file locations, [ Done ]
## allow RHOME to be set for non-default R etc
## comment this out if you need a different version of R,
## and set set R_HOME accordingly as an environment variable
R_HOME = $(shell R RHOME)
sources = $(wildcard *.cpp)
programs = $(sources:.cpp=)
## include headers and libraries for R
RCPPFLAGS = $(shell $(R_HOME)/bin/R CMD config --cppflags)
RLDFLAGS = $(shell $(R_HOME)/bin/R CMD config --ldflags)
RBLAS = $(shell $(R_HOME)/bin/R CMD config BLAS_LIBS)
RLAPACK = $(shell $(R_HOME)/bin/R CMD config LAPACK_LIBS)
## if you need to set an rpath to R itself, also uncomment
#RRPATH := -Wl,-rpath,$(R_HOME)/lib
## include headers and libraries for Rcpp interface classes
RCPPINCL = $(shell echo 'Rcpp:::CxxFlags()' | $(R_HOME)/bin/R --vanilla --slave)
RCPPLIBS = $(shell echo 'Rcpp:::LdFlags()' | $(R_HOME)/bin/R --vanilla --slave)
## include headers and libraries for RInside embedding classes
RINSIDEINCL = $(shell echo 'RInside:::CxxFlags()' | $(R_HOME)/bin/R --vanilla --slave)
RINSIDELIBS = $(shell echo 'RInside:::LdFlags()' | $(R_HOME)/bin/R --vanilla --slave)
## compiler etc settings used in default make rules
CXX = $(shell $(R_HOME)/bin/R CMD config CXX)
CPPFLAGS = -Wall $(shell $(R_HOME)/bin/R CMD config CPPFLAGS)
CXXFLAGS = $(RCPPFLAGS) $(RCPPINCL) $(RINSIDEINCL) $(shell $(R_HOME)/bin/R CMD
config CXXFLAGS)
LDLIBS = $(RLDFLAGS) $(RRPATH) $(RBLAS) $(RLAPACK) $(RCPPLIBS) $(RINSIDELIBS)
all: $(programs)
@test -x /usr/bin/strip && strip $^
run: $(programs)
@for p in $(programs); do echo; echo "Running $$p:"; ./$$p; done
clean:
rm -vf $(programs)
rm -vrf *.dSYM
runAll:
for p in $(programs); do echo "Running $$p"; ./$$p; done

Personally I have faced the same problem with a Makefile saved by some editor on Windows. The cause then was a BOM (Byte Order Mark) in the Makefile which was confusing Make.
To check if it is so you could (manually) copy and paste the whole Makefile (or maybe except for the header comment) into a new file created in some other editor/IDE. Also here is a great answer on how to remove BOM on Windows.