Rebuild BWA 0.7.3a for GCC7 (#13617)

* Add makefile patch for BWA 0.7.3a

* Fix patch

* Try one more time to get working patch

* Add dummy commit

recipes/bwa/0.7.3a/Makefile.patch

@@ -0,0 +1,13 @@
+diff --git a/Makefile b/Makefile
+index b660557..8891160 100644
+--- a/Makefile
++++ b/Makefile
+@@ -1,7 +1,6 @@
+-CC=			gcc
+ CFLAGS=		-g -Wall -O2
+ AR=			ar
+-DFLAGS=		-DHAVE_PTHREAD
++DFLAGS=		-DHAVE_PTHREAD $(LDFLAGS)
+ LOBJS=		utils.o kstring.o ksw.o bwt.o bntseq.o bwa.o bwamem.o bwamem_pair.o
+ AOBJS=		QSufSort.o bwt_gen.o bwase.o bwaseqio.o bwtgap.o bwtaln.o bamlite.o \
+ 			is.o bwtindex.o bwape.o kopen.o pemerge.o \

recipes/bwa/0.7.3a/meta.yaml

@@ -6,11 +6,13 @@ package:
   version: {{ version }}
 
 build:
-  number: 3
+  number: 4 
 
 source:
   url: http://downloads.sourceforge.net/project/bio-bwa/bwa-{{ version }}.tar.bz2
   sha256: {{ sha256 }}
+  patches:
+    - Makefile.patch 
 
 requirements:
   build: